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3,600 | Catheter stimulation of cardiac parasympathetic nerves in humans: a novel approach to the cardiac autonomic nervous system. | Cardiac parasympathetic nerves run alongside the superior vena cava (SVC) and accumulate particularly epicardially adjacent to the orifice of the coronary sinus (CS). In animals, these nerves can be electrically stimulated inside the SVC or CS, which results in negative chronotropic/dromotropic effects and negative inotropic effects in the atria but not the ventricles. Parasympathetic nerve stimulation (PS) with 20 Hz in the CS, however, also excites the atria, thereby inducing atrial fibrillation. The present study overcomes this limitation by applying high-frequency nerve stimuli within the atrial refractory period. Using this technique, we investigated for the first time whether neurophysiological effects similar to those in animals can be obtained in humans.</AbstractText>In 25 patients, parasympathetic nerves were stimulated via a multipolar electrode catheter placed in the SVC (stimulation with 20 Hz; n=14) or CS (pulsed 200-Hz stimuli; n=11). A significant sinus rate decrease and prolongation of the antegrade Wenckebach period was achieved during PS in the SVC. During PS in the CS, a graded-response prolongation of the antegrade Wenckebach interval was observed with increasing PS voltage until third-degree AV block occurred in 8 of 11 patients. The negative chronotropic/dromotropic effects started and terminated immediately after the onset and termination of PS, respectively. Atropine abolished these effects (n=11).</AbstractText>Human parasympathetic efferent nerve stimulation induces reversible negative chronotropic and dromotropic effects. PS may serve as an adjunctive tool for the diagnosis/treatment of supraventricular tachycardias and may be beneficial for ventricular rate slowing during tachycardic atrial fibrillation in patients with congestive heart failure.</AbstractText> |
3,601 | Life-threatening ventricular arrhythmias due to transient or correctable causes: high risk for death in follow-up. | This study evaluated the prognosis of patients resuscitated from ventricular tachycardia (VT) or ventricular fibrillation (VF) with a transient or correctable cause suspected as the cause of the VT/VF.</AbstractText>Patients resuscitated from VT/VF in whom a transient or correctable cause has been identified are thought to be at low risk for recurrence and often receive no primary treatment for their arrhythmias.</AbstractText>In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a potentially transient or correctable cause of VT/VF were not eligible for randomization. The mortality of these patients was compared with the mortality of patients with a known high risk of recurrence of VT/VF in the AVID registry.</AbstractText>Compared with patients having high risk VT/VF, those with a transient or correctable cause for their presenting VT/VF were younger and had a higher left ventricular ejection fraction. These patients were more often treated with revascularization as the primary therapy, more commonly received a beta-blocker, less often required therapy for congestive heart failure and less commonly received either an antiarrhythmic drug or an implantable cardioverter defibrillator. Nevertheless, subsequent mortality of patients with a transient or correctable cause of VT/VF was no different or perhaps even worse than that of the primary VT/VF population.</AbstractText>Patients identified with a transient or correctable cause for their VT/VF remain at high risk for death. Further research is needed to define truly reversible causes of VT/VF. Meanwhile, these patients may require more aggressive evaluation, treatment and follow-up than is currently practiced.</AbstractText> |
3,602 | Spontaneous coronary artery dissection in a pregnant woman. | Spontaneous coronary dissection is a rare condition occurring more often in women, with a higher frequency during the peripartum period. No specific etiology has been defined to describe this uncommon, yet often fatal phenomenon.</AbstractText>A young woman presented at 36 weeks of a noncomplicated pregnancy with recent onset of diaphoresis, dyspnea, and tingling substernal chest discomfort. Upon evaluation, she developed cardiovascular collapse and ventricular fibrillation requiring aggressive resuscitative measures, eventually leading to extracorporeal membrane oxygenation. Right coronary artery dissection was ultimately diagnosed and treated with intracoronary angioplasty and stent placement.</AbstractText>Spontaneous coronary dissection must be considered when evaluating a patient with a similar clinical presentation, given its overall mortality of more than 50% at presentation, particularly in the peripartum period.</AbstractText> |
3,603 | [Interesting cases of ventilatory therapy of sleep apnea in a group of our patients]. | In the group of patients investigated in our sleep laboratory and successfully treated by positive pressure applied in to the upper airways through nasal mask (nCPAP) some interesting cases appeared. These cases show beneficial effect of nCPAP therapy, unfortunately not widely spread and recognized in our country. These patients were unsuccessfully treated before by conventional methods, which did not improve their situation for a longer time. Only after polysomnography carried out in our sleep laboratory and after home treatment with nCPAP or BiPAP machine, the situation radically improved.</AbstractText>In a director of important enterprise after unrelated car accident atrial fibrillation caused by dilation was discovered, which did not respond even on Electro cardioversion. After recognition of severe obstructive sleep apnoea syndrome (OSAS) this patient was treated successfully by BiPAP. The second case: a bus driver, who falls asleep on the traffic light with full buss of passengers. A diagnose OSAS with a multiple sleep latency test result below 2.5 minutes. The nCPAP treatment allowed him to continue to work, but transiently on different position. The third: 40-year-old patient with a body mass index (BMI) 38 and with dysrhythmias IIIb-IVb according to Lown. The respiratory disturbance index (RDI) was 40 and oxygen desaturation bellow 77%. There was bigeminia on ECG. During four hour with nCPAP treatment there was only two randomly ventricular extrasystols appeared, confirming the beneficial effect of treatment. These cases demonstrate a wide spectrum of cardiac dysrhythmias, which have only functional character, but are important for the practice. The demonstrated cases highlighted the importance of home nCPAP therapy in OSAS patients.</AbstractText> |
3,604 | Iterative atrial tachycardia originating from the coronary sinus musculature. | A case of iterative atrial tachycardia leading to dilated cardiomyopathy is reported. During electrophysiologic study, the tachycardia showed a markedly irregular cycle length associated with changes in atrial activation breakthrough as demonstrated by coronary sinus (CS) recordings and frequently degenerated into self-terminating atrial fibrillation. Left atrial transseptal mapping demonstrated the earliest endocardial atrial activation close to the posterolateral mitral annulus, but this was invariably later than that recorded within the CS, where low-energy radiofrequency applications eliminated the tachycardia. No acute vessel damage was observed at postablation CS angiography. In accordance with previously published experimental data, we hypothesized that the muscular sleeves surrounding the CS might be involved in the genesis of this tachycardia. During 6-month follow-up, the patient remained asymptomatic without tachycardia recurrences and with complete recovery of left ventricular function, confirming the reversible nature of the tachycardia-induced cardiomyopathy. |
3,605 | Mechanisms by which AC leakage currents cause complete hemodynamic collapse without inducing fibrillation. | The first study of weak alternating current (AC) stimulation in closed chest humans showed that complete hemodynamic collapse can occur below the threshold for inducing ventricular fibrillation (VF), a heretofore unknown danger to patients. This article, and the accompanying simulation article, explore the mechanisms responsible for the collapse.</AbstractText>A quadripolar pacing catheter was placed in the right ventricle (RV) of six dogs. The tip of the catheter (17 mm2) carried 5 seconds of AC stimulation ranging from 10 to 160 Hz and 10 to 1,000 microA. The lead II body surface ECG, femoral artery pressure, and a bipole from the proximal pair of electrodes on the RV catheter were recorded 2 seconds before, during, and 2 seconds after stimulation. Based on the blood pressure, every episode was categorized as VF, COLLAPSE without VF, extrasystolic without COLLAPSE (EFFECT), or having caused no effect (NSR). The electrical activation interval (interspike interval [ISI]) from the RV bipole was compared with the mechanical activation interval, determined from M-mode ultrasound. COLLAPSE is associated with a short ISI (NSR = 408+/-110 msec; EFFECT = 305+/-113 msec; COLLAPSE = 179+/-25 msec; P < 0.001) with a high degree of regularity (P < 0.001): coefficient of variation of ISI for COLLAPSE (0.038+/-0.069) versus VF (0.389+/-0.222), EFFECT (0.420+/-0.241), and NSR (0.016+/-0.048). Electrical activation and mechanical activation rates occurred at integer multiples of the AC stimulation period.</AbstractText>COLLAPSE (86+/-37 microA; minimum 50 microA in two animals) occurs below the VF threshold (108+/-28 microA) by causing rapid, regular excitation.</AbstractText> |
3,606 | Excitation of a cardiac muscle fiber by extracellularly applied sinusoidal current. | The goal of this study was to examine the effect of AC currents on a cardiac fiber. The study is the second in a series of two articles devoted to the subject. The initial study demonstrated that low-strength sinusoidal currents can cause hemodynamic collapse without inducing ventricular fibrillation. The present modeling study examines possible electrophysiologic mechanisms leading to such hemodynamic collapse.</AbstractText>A strand of cardiac myocytes was subjected to an extracellular sinusoidal current stimulus. The stimulus was located 100 microm over one end. Membrane dynamics were described by the Luo-Rudy dynamic model. Examination of the interspike intervals (ISI) revealed that they were dependent on the phase of the stimulus and, as a result, tended to take on discrete values. The frequency dependency of the current threshold to induce an action potential in the cable had a minimum, as has been found experimentally. When a sinus beat was added to the cable, the sinus beat dominated at low-stimulus currents, whereas at high currents the time between action potentials corresponded to the rate observed in a cable without the sinus beat. In between there was a transition region with a wide dispersion of ISIs.</AbstractText>The following phenomena observed in the initial study were reproduced and explained by the present simulation study: insignificant effect of temporal summation of subthreshold stimuli, frequency dependency of the extrasystole threshold, discrete nature of the ISI, and increase in regularity of the ISI with increasing stimulus strength.</AbstractText> |
3,607 | Conversion of atrial fibrillation by the experimental antiarrhythmic drug tedisamil in two canine models. | Tedisamil is an experimental bradycardic agent possessing action potential-prolonging effects. It has been proven effective in terminating ventricular arrhythmias in several animal models and atrial flutter in a conscious dog model. There are no reports to date evaluating tedisamil's efficacy in terminating atrial fibrillation (AF).</AbstractText>Two different canine models of AF were used. One group of dogs (n = 6) was subjected to 28 days of chronic fibrillatory pacing at 50 Hz using an implantable neural stimulator. Sustained AF was achieved in all dogs within 14 days of initiating pacing. A second set of dogs (n = 5) had AF induced via bilateral vagal stimulation. Tedisamil 1 mg/kg was 100% effective in terminating AF in both models. Cardioversion was associated with a statistically significant prolongation of the fibrillatory cycle length immediately before return to normal sinus rhythm in both models. A dose-response trial was performed in the vagal AF group as well as in a second group of three dogs that underwent chronic fibrillatory pacing. The efficacy of tedisamil was dose dependent, with limited efficacy at 0.1 and 0.3 mg/kg intravenously in both models. Tedisamil was able to prevent reinduction of sustained AF 30 minutes after administration of 1 mg/kg in the chronic pacing model in all dogs. Side effects included minor hypersalivation in most dogs receiving the 1 mg/kg dose. No ventricular ectopy or arrhythmias were observed.</AbstractText>Tedisamil is effective for conversion of sustained AF to normal sinus rhythm in two different models of AF.</AbstractText> |
3,608 | Relationship between serum potassium concentration and risk of recurrent ventricular tachycardia or ventricular fibrillation. | Electrolyte abnormalities are considered a correctable cause of a life-threatening ventricular arrhythmia according to American Heart Association/American College of Cardiology Practice Guidelines, and ventricular tachycardia or ventricular fibrillation in the setting of an electrolyte abnormality is considered a class III indication for defibrillator implantation. However, there are little data to support this recommendation. The purpose of this study was to determine the risk of a recurrent sustained ventricular arrhythmia in patients with a low serum potassium concentration at the time of an initial episode of a sustained ventricular arrhythmia.</AbstractText>One hundred sixty-nine consecutive patients who presented with a sustained ventricular arrhythmia and a serum potassium concentration determined on the day of the arrhythmia underwent defibrillator implantation. All patients had structural heart disease and left ventricular ejection fraction of 0.32+/-0.15. On the day of the index arrhythmia, 30% of the patients had a serum potassium concentration <3.5 or >5.0 mEq/L, including 7% who had a serum potassium concentration <3.0 or >6.0 mEq/L. For the entire cohort of patients, freedom from a recurrent sustained ventricular arrhythmia was 18% at 5 years and was not significantly different among patients with a serum potassium concentration <3.5 mEq/L (23%), between 3.5 and 5.0 mEq/L (16%), and >5.0 mEq/L (5%; P = 0.1).</AbstractText>The results of the present study suggest that patients with structural heart disease and an abnormal serum potassium concentration at the time of an initial episode of sustained ventricular tachycardia or ventricular fibrillation are at high risk for a recurrent ventricular arrhythmia; therefore, implantable defibrillator therapy may be reasonable.</AbstractText> |
3,609 | Supraventricular arrhythmias in children and young adults with implantable cardioverter defibrillators. | Rapidly conducted supraventricular tachycardias (SVTs) can lead to inappropriate device therapy in implantable cardioverter defibrillator (ICD) patients. We sought to determine the incidence of SVTs and the occurrence of inappropriate ICD therapy due to SVT in a pediatric and young adult population.</AbstractText>We undertook a retrospective review of clinical course, Holter monitoring, and ICD interrogations of patients receiving ICD follow-up at our institution between March 1992 and December 1999. Of 81 new ICD implantations, 54 eligible patients (median age 16.5 years, range 1 to 48) were identified. Implantation indications included syncope and/or spontaneous/inducible ventricular arrhythmia with congenital heart disease (30), long QT syndrome (9), structurally normal heart (ventricular tachycardia/ventricular fibrillation [VT/VF]) (7), and cardiomyopathies (7). Sixteen patients (30%) received a dual-chamber ICD. SVT was recognized in 16 patients, with 12 of 16 having inducible or spontaneous atrial tachycardias. Eighteen patients (33%) received > or =1 appropriate shock(s) for VT/VF; 8 patients (15%) received inappropriate therapy for SVT. Therapies were altered after an inappropriate shock by increasing the detection time or rate and/or increasing beta-blocker dosage. No single-chamber ICD was initially programmed with detection enhancements, such as sudden onset, rate stability, or QRS discriminators. Only one dual-chamber defibrillator was programmed with an atrial discrimination algorithm. Appropriate ICD therapy was not withheld due to detection parameters or SVT discrimination programming.</AbstractText>SVT in children and young adults with ICDs is common. Inappropriate shocks due to SVT can be curtailed even without dual-chamber devices or specific SVT discrimination algorithms.</AbstractText> |
3,610 | Dilated Cardiomyopathy. | The management of patients with dilated cardiomyopathy (DCM) heart failure starts with the determination of the underlying diagnosis, definition of the hemodynamic character (eg, systolic, diastolic, valvular, right- and left-sided heart dysfunction), recognition of complicating factors (eg, atrial fibrillation, renal dysfunction), and consideration for any surgically remedial lesions (eg, severe valvular regurgitation, high-grade coronary artery occlusive disease). Angiotensin-converting enzyme inhibitors, beta-blocking agents, digoxin, and judicious diuretic administration make up the therapeutic plan for patients with symptomatic DCM heart failure. Angiotensin-converting enzymes are indicated for patients with DCM who have mild or no detectable symptoms; whether this subgroup would benefit from long-term beta-blockade remains to be established. Spirolactone also has been shown to be effective in patients with more advanced stages of heart failure. Biventricular pacing (cardiac resynchronization therapy) recently has been approved for use in patients with DCM and a left ventricular or intraventricular conduction defect and a QRS duration of longer than 140 msec. More intense pharmacotherapy, mechanical devices, and transplantation are directed at patients with severely symptomatic end-stage DCM. The effectiveness of any heart failure treatment plan is very much dependent on nonpharmacologic approaches, including dietary measures, exercise conditioning, and similar considerations, all of which are best delivered by dedicated heart failure programs. |
3,611 | alpha-Methylnorepinephrine, a selective alpha2-adrenergic agonist for cardiac resuscitation. | The purpose of this study was to investigate the effects of a selective alpha2-adrenergic agonist, alpha-methylnorepinephrine (alphaMNE) as an alternative vasopressor agent during cardiopulmonary resuscitation (CPR).</AbstractText>For more than 40 years, epinephrine has been the vasopressor agent of choice for CPR. Its beta- and alpha1-adrenergic effects increase myocardial oxygen consumption, magnify global myocardial ischemia and increase the severity of postresuscitation myocardial dysfunction.</AbstractText>Ventricular fibrillation (VF) was induced in 20 Sprague-Dawley rats. After 8 min of untreated VF, mechanical ventilation and precordial compression began. AlphaMNE, epinephrine or saline placebo was injected into the right atrium 2 min after the start of precordial compression. As an additional control, one group of animals was pretreated with alpha2-receptor blocker, yohimbine, before injection of alphaMNE. Defibrillation was attempted 4 min later. Left ventricular pressure, dP/dt40, negative dP/dt and cardiac index were measured for an interval of 240 min after resuscitation.</AbstractText>Except for saline placebo and yohimbine-treated animals, comparable increases in coronary perfusion pressure were observed after each drug intervention. All animals were successfully resuscitated. Left ventricular diastolic pressure, cardiac index, dP/dt40 and negative dP/dt were more optimal after alphaMNE; this was associated with significantly better postresuscitation survival. Pretreatment with vohimbine abolished the beneficial effects of alphaMNE.</AbstractText>The selective alpha2-adrenergic agonist, alphaMNE, was as effective as epinephrine for initial cardiac resuscitation but provided strikingly better postresuscitation myocardial function and survival.</AbstractText> |
3,612 | Alterations in potassium channel gene expression in atria of patients with persistent and paroxysmal atrial fibrillation: differential regulation of protein and mRNA levels for K+ channels. | Our purpose was to determine whether patients with persistent atrial fibrillation (AF) and patients with paroxysmal AF show alterations in potassium channel expression.</AbstractText>Persistent AF is associated with a sustained shortening of the atrial action potential duration and atrial refractory period. Underlying molecular changes have not been studied in humans. We investigated whether a changed gene expression of specific potassium channels is associated with these changes in patients with persistent AF and in patients with paroxysmal AF.</AbstractText>Right atrial appendages were obtained from 8 patients with paroxysmal AF, 10 with persistent AF and 18 matched controls in sinus rhythm. All controls underwent coronary artery bypass surgery, whereas most AF patients underwent Cox's MAZE surgery (atrial arrhythmia surgery to cure AF) (n = 12). All patients had normal left ventricular function. mRNA (ribonucleic acid) levels were measured by semiquantitative polymerase chain reaction and protein content by Western blotting.</AbstractText>mRNA levels of transient outward channel (Kv4.3), acetylcholine-dependent potassium channel (Kir3.4) and ATP-dependent potassium channel (Kir6.2) were reduced in patients with persistent AF (-35%, -47% and -36%, respectively, p < 0.05), whereas only Kv4.3 mRNA level was reduced in patients with paroxysmal AF (-29%, p = 0.03). No changes were found for Kv1.5 and HERG mRNA levels in either group. Protein levels of Kv4.3, Kv1.5 and Kir3.1 were reduced both in patients with persistent AF (-39%, -84% and -47%, respectively, p < 0.05) and in those with paroxysmal AF (-57%, -64%, and -40%, respectively, p < 0.05).</AbstractText>Persistent AF is accompanied by reductions in mRNA and protein levels of several potassium channels. In patients with paroxysmal AF these reductions were observed predominantly at the protein level and not at the mRNA level, suggesting a post-transcriptional regulation.</AbstractText> |
3,613 | The repolarization-excitability relationship in the human right atrium is unaffected by cycle length, recording site and prior arrhythmias. | The goal of this study was to determine the relationship between repolarization and excitability in the human atrium under various conditions.</AbstractText>Action potential duration (APD) measurements from monophasic action potential (MAP) recordings provide a surrogate for measuring the effective refractory period (ERP) in human ventricle. The relationship between repolarization and refractoriness in human atrium and the effect of prior atrial fibrillation/flutter on the ERP/APD correlation are unknown.</AbstractText>Seven patients with sinus rhythm and 15 patients after conversion of atrial flutter or fibrillation were evaluated. Monophasic action potentials were recorded at multiple right atrial sites and during different basic cycle lengths from 300 to 700 ms, while ERPs were determined by extrastimulus technique using the MAP recording-pacing combination catheter.</AbstractText>There was a close correlation between ERP and APD at 70% repolarization (APD70, r = 0.97; p < 0.001) and 90% repolarization (APD90, r = 0.98; p < 0.001), respectively. Refractoriness occurred at a repolarization level of 72 +/- 8%. The ERP/APD70 and ERP/APD90 ratios averaged 1.06 +/- 0.10 and 0.86 +/- 0.08, respectively. These ratios were nearly constant over the entire range of basic cycle lengths, between different sites in individual patients and between different patients. Patients cardioverted from atrial fibrillation or flutter exhibited no significant differences in the ERP/APD relationship compared with patients with sinus rhythm.</AbstractText>Effective refractory period and APD are closely related in the human right atrium. Using the MAP recording technique, atrial ERPs can be assessed by measurement of APDs. Effective refractory period is most closely reflected by APD70. Thus, MAP recordings allow investigation of the local activation and repolarization time course beat by beat, visualizing the excitable gap.</AbstractText> |
3,614 | Echocardiographic evaluation of right cardiac function in patients with chronic pulmonary diseases. | It is clinically important to evaluate the severity of right ventricular (RV) overload in patients with chronic pulmonary diseases (CPD). For such evaluation, echocardiography has been widely used because the procedure is noninvasive and can be performed repeatedly. We evaluated the severity of RV overload in CPD patients to assess the usefulness of pulsed Doppler echocardiography. The A/E ratio and deceleration time of early RV inflow velocity correlated significantly with the mean pulmonary artery pressure (MPAP) both in patients with and without CPD. The acceleration time/RV ejection time (AcT/RVET) was significantly lower in CPD patients than control subjects and correlated significantly with MPAP. Furthermore, AcT/RVET improved in patients with mild respiratory failure after oxygen therapy, along with a decrease in MPAP. We also compared the new index of myocardial performance (NI) in control subjects and patients with pulmonary tuberculosis sequelae (TB) undergoing home oxygen therapy. The NI was significantly higher in the TB group. Although these results were satisfactory, the pulsed Doppler echocardiography has certain disadvantages because monitoring is influenced by anatomical factors and it is difficult to perform in patients with atrial fibrillation or tachycardia. We conclude that echocardiography using a Doppler method is a useful noninvasive technique for assessment of the right heart system. The precision of this procedure can be improved by combination with other echocardiographic indices of RV overload. |
3,615 | Effect of Sotalol in the prevention of atrial fibrillation following coronary artery bypass grafting. | We assessed the efficacy of postoperatively administered oral Sotalol in preventing the occurrence of postoperative atrial fibrillation.</AbstractText>Subjects were 80 consecutive patients undergoing coronary artery bypass grafting (CABG) randomized alternately into a Sotalol group (40 patients) administered 80 mg of oral Sotalol daily starting on the postoperative day 1 and continued for 14 days, and a control group (40 patients) matched for age and gender.</AbstractText>The incidence of postoperative atrial fibrillation (21 patients) was significantly lower in the Sotalol group (6/40 patients; 15%) than in controls (15/40; 37.5%) (p < 0.05). Significant bradycardia or hypotension, necessitating drug withdrawal, occurred in 3 of 40 (7.5%) patients in the Sotalol group. None in the Sotalol group developed Torsardes de Pointes or sustained ventricular arrhythmias or other severe side effects. The sinus heart rate increased in both groups but less in the Sotalol group. QT, QRS, and QTc durations did not differ between groups. Postoperative hospital stay did not differ between groups.</AbstractText>Oral Sotalol administration of 80 mg daily was associated with a significant decrease in postoperative atrial fibrillation in patients undergoing CABG without appreciable side effects. Sotalol should thus be considered in preventing postoperative atrial fibrillation in patients undergoing CABG in the absence of heart failure and significant left ventricular dysfunction.</AbstractText> |
3,616 | Preinfarction angina protects against out-of-hospital ventricular fibrillation in patients with acute occlusion of the left coronary artery. | The goal of this study was to evaluate the effect of preconditioning on out-of-hospital ventricular fibrillation (VF) in patients with acute myocardial infarction (AMI).</AbstractText>More than half of the deaths associated with AMI occur out of the hospital and within 1 h of symptom onset. In humans, preinfarction angina (PA), which can serve as a surrogate marker for preconditioning, reduces infarct size, but the protective effect against out-of-hospital VF has not been investigated.</AbstractText>Preinfarction angina status and acute coronary angiographic findings of 72 consecutive patients with AMI complicated by out-of-hospital VF were compared with 144 matched controls without this complication.</AbstractText>Preinfarction angina is associated with a lower risk for VF (odds ratio [OR]: 0.40, 95% confidence interval [CI]: 0.18 to 0.88). In patients with acute occlusion of the left coronary artery (LCA) (n = 136), the risk reduction is pronounced (OR: 0.25, 95% CI: 0.10 to 0.66), whereas, in patients with acute occlusion of the right coronary artery (RCA) (n = 67), the protective effect of PA on VF was not observed (OR: 2.25, 95% CI: 0.45 to 11.22). Subgroup and multivariate analyses show that the protective effect is independent of cardiovascular risk factors, preinfarction treatment with beta-adrenergic blocking agents or aspirin, the presence of collaterals or residual antegrade flow or the extent of coronary artery disease.</AbstractText>Preinfarction angina protects against out-of-hospital VF in patients with acute occlusion of the LCA. This protection is independent of risk factors or coronary anatomy. A larger study is needed to examine the apparently different effect in patients with acute occlusion of the RCA.</AbstractText> |
3,617 | Clinical profile of arrhythmogenic right ventricular cardiomyopathy in Chinese patients. | To study the clinical profile of Chinese patients with arrhythmogenic right ventricular cardiomyopathy (ARVC).</AbstractText>Chinese patients who fulfilled the diagnostic criteria of ARVC proposed by the Task Force of the European Society of Cardiology and of the scientific council on cardiomyopathy of the International Society and Federation of Cardiology were recruited for analysis.</AbstractText>Clinical data of patients with ARVC including age, sex, family history, presenting symptoms, electrocardiograph (ECG), echocardiography, cardiac catheterization, magnetic resonance imaging (MRI), electrophysiology study (EPS) and therapeutic intervention were analyzed.</AbstractText>Eleven patients (seven males) were diagnosed with ARVC. Mean age at clinical presentation was 42.6+/-14.8 years. Two patients (18.1%) had positive family history of ARVC or premature sudden cardiac death. The commonest presenting symptoms were palpitation (73%) and dizziness (46%). Spontaneous ventricular tachycardia (VT) was the presenting arrhythmia in 54% and 1 (9%) with ventricular fibrillation and cardiac arrest. Seven patients (64%) had the ECG abnormality as defined by the Task Force. Echocardiography showed right ventricular (RV) dilatation in five patients (46%) and all patients had normal left ventricular function. Nine patients (90%) had RV wall thinning or fibrofatty replacement on MRI examination. Inducible monomorphic VT was detected in four out of nine patients at EPS. All eight patients had normal coronary arteries and left ventriculogram but RV dilatation and global hypokinesia was seen in three patients. Implantable cardioverter defibrillators were implanted in five patients and two of them had shocks delivered during the follow-up period.</AbstractText>In this study, familial incidence of premature sudden death in patients with ARVC appears to be low and left ventricular involvement in affected individuals is uncommon. MRI is still the best investigation for ARVC.</AbstractText> |
3,618 | Myocardial protection: the efficacy of an ultra-short-acting beta-blocker, esmolol, as a cardioplegic agent. | During myocardial revascularization, some surgeons (particularly in the United Kingdom) use intermittent crossclamping with fibrillation as an alternative to cardioplegia. We recently showed that intermittent crossclamping with fibrillation has an intrinsic protection equivalent to that of cardioplegia. In this study we hypothesized that arrest, rather than fibrillation, during intermittent crossclamping may be beneficial. Because esmolol, an ultra-short-acting beta-blocker, is known to attenuate myocardial ischemia-reperfusion injury, we compared the protective effect of esmolol arrest with that of intermittent crossclamping with fibrillation and conventional cardioplegia (St Thomas' Hospital solution).</AbstractText>Isolated rat hearts were Langendorff perfused at either constant flow (14 mL/min) or constant pressure (75 mm Hg) with oxygenated Krebs-Henseleit bicarbonate buffer (37 degrees C), and left ventricular developed pressure was assessed. In study 1 (constant flow perfusion) 8 groups (n = 6 hearts per group) were studied: (1) 40 minutes of global ischemia; (2) 2 minutes of St Thomas' Hospital infusion and 40 minutes of ischemia; (3) multidose (every 10 minutes) infusions of St Thomas' Hospital solution during 40 minutes of ischemia; (4) 2 minutes of esmolol infusion and 40 minutes of ischemia; (5) multidose (every 10 minutes) esmolol infusions during 40 minutes of ischemia; (6) continuous infusion of esmolol for 40 minutes during coronary perfusion; (7) intermittent (4 x 10 minutes) ischemia with ventricular fibrillation; and (8) intermittent (4 x 10 minutes) ischemia preceded by intermittent esmolol administration. All protocols were followed by 60 minutes of reperfusion. Further experiments (study 2) examined the esmolol administration method in hearts perfused by constant pressure.</AbstractText>An optimal arresting dose of 1.0 mmol/L esmolol was established. In study 1 recovery of left ventricular developed pressure (expressed as percentage of preischemic value) was 7% +/- 4%, 28% +/- 8%, 70% +/- 5%, 8% +/- 1%, 90% +/- 4%, 65% +/- 3%, 71% +/- 5%, and 76% +/- 5% in groups 1 to 8, respectively. Intermittent esmolol arrest with global ischemia provided equivalent myocardial protection to intermittent crossclamping with fibrillation, continuous esmolol perfusion, and multidose St Thomas' Hospital solution. Surprisingly, multidose esmolol infusion was more protective than all other treatments. In further experiments (study 2) optimal recovery was obtained with multiple esmolol infusions (by constant flow or constant pressure), but continuous esmolol infusion (at constant flow) was less effective than constant pressure infusion.</AbstractText>Intermittent arrest with esmolol did not enhance protection of intermittent crossclamping with fibrillation; however, multiple esmolol infusions during global ischemia provided improved protection. Administration (constant flow or constant pressure) of arresting solutions influenced outcome only during continuous infusion. Multidose esmolol arrest may be a beneficial alternative to intermittent crossclamping with fibrillation or conventional cardioplegia.</AbstractText> |
3,619 | A comparison of the QT and QTc dispersion among patients with sustained ventricular tachyarrhythmias and different etiologies of heart disease. | To determine if etiology of heart disease is associated with differences in QT and QTc dispersion among patients with ventricular tachyarrhythmias.</AbstractText>This study was undertaken in 145 patients undergoing electrophysiological testing for sustained ventricular tachycardia or ventricular fibrillation. Patients were divided into groups based on etiology of heart disease determined by history, ECG, coronary angiography, and echocardiography. The groups included patients with: dilated cardiomyopathy (n = 29), myocardial infarction (n = 90), established coronary artery disease without a myocardial infarction (n = 11), or hypertension induced left ventricular hypertrophy (n = 15). The QT intervals on a 12--lead ECG were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QT(c) interval from the longest on each 12-lead recording.</AbstractText>The patients with dilated cardiomyopathy had significantly higher QT and QTc dispersion values as compared to any of the other three groups (P < 0.05 for both). No other differences in electrocardiographic variables were found between groups.</AbstractText>In a group of patients with a history of ventricular tachycardia or ventricular fibrillation, QT and QTc dispersion are significantly greater among patients with dilated cardiomyopathy than for patients with a previous myocardial infarction, established coronary artery disease without a myocardial infarction, or hypertensive left ventricular hypertrophy.</AbstractText> |
3,620 | Surgically treated primary lung cancer associated with Brugada syndrome: report of a case. | A 71-year-old man with primary lung cancer associated with Brugada syndrome was safely operated on following the placement of an implantable cardioverter defibrillator (ICD). During examinations for Brugada syndrome, a tumor in the apicoposterior segment of the left lung was incidentally detected by chest computed tomography. Following the implantation of an ICD, surgical treatment of the left lung tumor was scheduled. A lung biopsy was thoracoscopically performed and adenocarcinoma was diagnosed based on a frozen section analysis. A left upper lobectomy with lymph node dissection was performed through a standard posterolateral thoracotomy. Ventricular fibrillation, which occurred during the night of the first day following surgery, was successfully managed by the ICD. |
3,621 | Effects of bystander first aid, defibrillation and advanced life support on neurologic outcome and hospital costs in patients after ventricular fibrillation cardiac arrest. | To evaluate the effects of basic life support, time to first defibrillation and emergency medical service arrival time on neurologic outcome and expenses for hospital care in patients after cardiac arrest.</AbstractText>Large urban emergency medical services system and emergency department in a 2000-bed university hospital.</AbstractText>Outcome and cost benefit analysis of patients admitted to the hospital after witnessed, out-of-hospital, ventricular fibrillation cardiac arrest from October 1, 1991, until December 31, 1997.</AbstractText>Out of 1054 patients with out-of-hospital cardiac arrest, 276 were eligible.</AbstractText>The effects of basic and advanced life support measures on neurologic outcome and hospital expenses were evaluated. In contrast to intubation (odds ratio 1.08; 95% CI: 0.51-2.31; p=0.84), basic life support (odds ratio 0.44; 95% CI: 0.24-0.77; p=0.004) and time to first defibrillation (odds ratio 1.08; 95% CI: 1.03-1.13; p=0.001) were significantly correlated with good neurologic outcome. Among the patients who did not receive basic life support, the average cost per patient with good neurologic outcome significantly increased with the delay of the first defibrillation (p<0.001).</AbstractText>In contrast to intubation, bystander basic life support and time to first defibrillation were significantly associated with good neurologic outcome and resulted in fewer expenses spent on in-hospital efforts.</AbstractText> |
3,622 | Incidence and type of cardiac arrhythmias in critically ill patients: a single center experience in a medical-cardiological ICU. | To determine the frequency and types of significant, sustained arrhythmias in a mixed ICU.</AbstractText>Prospective, observational study in a medical-cardiological-postoperative ICU at a university hospital.</AbstractText>133 consecutive patients with arrhythmias.</AbstractText>All patients had continuous ECG monitoring and automatic arrhythmia detection. We assessed: (a) sustained (>30 s) tachyarrhythmias; (b) all tachyarrhythmias requiring therapy; (c) bradycardias of fewer than 40 beats/min or requiring intervention. There were 310 arrhythmia episodes: 278 tachyarrhythmias (108 narrow-QRS complex, 168 wide-QRS complex; 179 regular, 97 irregular) and 32 bradycardias. Of the 278 tachycardias in 54 patients, 135 (48.6%) were ventricular. There were 13 episodes of torsade de pointes (4.67%) in five patients. Of the 278 tachycardiac episodes 83 were atrial fibrillation (29.8%, 63 patients), 10 atrial flutter (3.6%, 8 patients), 21 supraventricular tachycardias (7.55%, 7 patients), and 2 ectopic junctional tachycardia (0.72%, 1 patient). The number of patients showing significant arrhythmias was comparable over the years (11-12/1996: 4/28 [14.3], 1997: 52/302 [17.2%], 1998: 55/286 [19.2%], 22/140 [15.7%] 1-7/1999). The ICU stay was significantly longer in arrhythmia patients than in 623 patients without arrhythmias (median 4 vs. 14 days), and there was a trend towards higher mortality (40/133, 30.8%, vs. 132/623, 21.2%, P=0.061, log-rank).</AbstractText>Only one-fifth of patients in this mixed ICU had significant arrhythmias, taking a contemporary definition of arrhythmias. Ventricular tachycardia and atrial fibrillation were the most frequent arrhythmias.</AbstractText> |
3,623 | Electromechanical dysfunction of the left atrium associated with interatrial block. | Our purpose was to determine the effect of interatrial block (IAB, P-wave duration >/=120 ms) on left atrial (LA) dynamics. IAB is associated with LA enlargement (LAE). LA dysfunction is associated with decreased left ventricular filling, a propensity for LA appendage thrombus formation, and reduced atrial natriuretic peptide levels. We evaluated LA function in patients with and without IAB matched for LA size.</AbstractText>Echocardiograms with LA enlargement were analyzed. Twenty-four patients had IAB, and 16 patients without IAB formed the control group. LA volumes, A-wave acceleration times (At), LA stroke volume (LASV), ejection fraction (LAEF), and kinetic energy (LAKE) were calculated.</AbstractText>The control group and patients with IAB had comparable maximal LA volume and diameter (P >.05). Patients with IAB had significantly longer At (115 +/- 39 ms vs 83 +/- 24 ms, P <.01) and smaller LASV (7 +/- 5 mL vs 17 +/- 6 mL, P <.01), LAEF (9% +/- 6% vs 25% +/- 8%, P <.01), and LAKE (20 +/- 14 vs 65 +/- 44 Kdyne/cm/s, P <.01). LAKE varied inversely with P-wave duration (r = -0.51, P <.01). P-wave duration and minimal LA volume were independent determinants of LAEF.</AbstractText>Patients with IAB have a sluggish, poorly contractile LA, and the extent of dysfunction is related to the degree of electrical delay from IAB. IAB should be considered a marker of an electromechanically dysfunctional LA and hence a risk factor for atrial fibrillation and congestive heart failure.</AbstractText> |
3,624 | Comparison of dilated cardiomyopathy and coronary artery disease in patients with life-threatening ventricular arrhythmias: Differences in presentation and outcome in the AVID registry. | The etiology of structural heart disease in patients with life-threatening arrhythmias (ventricular tachycardia [VT]/ventricular fibrillation [VF]) may define clinical characteristics at presentation, may require that different therapies be administered, and may cause different mortality outcomes.</AbstractText>In the Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, baseline clinical characteristics, treatments instituted, and ultimate mortality outcomes from the National Death Index were obtained on 3117 patients seen at participating institutions with VT/VF, irrespective of participation in the randomized trial. By use of these data, 2268 patients with coronary artery disease (CAD) were compared with 334 patients with dilated nonischemic cardiomyopathy (DCM).</AbstractText>The CAD group was 7 years older and had a higher percentage of males. DCM patients were more likely to be African American, have severely compromised left ventricular function (52% vs 39%), and have a history of congestive heart failure symptoms (62% vs 44%). Patients with CAD were more likely to be treated with b-blockers and calcium channel blockers and less likely to be treated with angiotensin-converting enzyme inhibitors. Patients with DCM were more likely to be treated with diuretics, warfarin, and an implantable cardioverter defibrillator for VT/VF (54% vs 48% for CAD); the use of other antiarrhythmic therapies did not differ between the 2 groups. Two-year survival was not significantly different between the groups (76.6% [95% CI 74.6%-78.7%] vs 78.2% [95% CI 73.6%-82.9%]).</AbstractText>In AVID registry patients with VT/VF, demographic and clinical characteristics were different between patients with CAD and those with DCM. Despite these differences, overall survival was similar in these 2 groups.</AbstractText> |
3,625 | Amiodarone versus a beta-blocker to prevent atrial fibrillation after cardiovascular surgery. | Both amiodarone and beta-blockers have been shown to decrease the incidence of atrial fibrillation after cardiovascular surgery. However, the superior agent has not been identified.</AbstractText>We performed a pilot study on 102 patients (68 men, mean age 65 +/- 10 years, mean left ventricular ejection fraction 0.53 +/- 0.12) undergoing cardiovascular surgery (94 coronary artery bypass grafting [CABG], 5 valvular surgery only, and 3 CABG + valvular surgery). The patients were randomized to receive amiodarone (1 g/d intravenously x 48 hours, then 400 mg/d orally until discharge) or propranolol (1 mg intravenously every 6 hours x 48 hours, then 20 mg orally four times a day until discharge). Atrial fibrillation was defined as lasting longer than 1 hour or resulting in hemodynamic compromise.</AbstractText>The incidence of postoperative atrial fibrillation was 16.0% (8/50) in the amiodarone group and 32.7% (17/52) in the propranolol group (P =.05). The mean length of stay was 8.8 +/- 3.5 days for amiodarone-treated patients and 8.4 +/- 2.7 days for propranolol-treated patients (P not significant). Serious adverse events were uncommon and similar in each group.</AbstractText>Early intravenous amiodarone, followed by oral amiodarone, appears to be superior to propranolol in the prevention of postoperative atrial fibrillation. It is well tolerated and can be started at the time of surgery. However, the use of amiodarone did not result in a reduction in the length of hospital stay.</AbstractText> |
3,626 | Treatment of the elderly post-myocardial infarction patient. | Coronary risk factors should be modified in older persons after myocardial infarction (MI). Aspirin 160-325 mg daily and beta blockers should be administered indefinitely. Anticoagulants should be administered post-MI to patients unable to tolerate daily aspirin, to those with persistent atrial fibrillation, and to those with left ventricular thrombus. Nitrates, along with beta blockers, should be used to treat angina pectoris. Angiotensin-converting enzyme inhibitors should be administered after MI to patients who have congestive heart failure, an anterior MI, or a left ventricular ejection fraction of at or below 40%. There are no class I indications for the use of calcium channel blockers after MI. Complex ventricular arrhythmias should be treated with beta blockers. Persons with life-threatening ventricular tachycardia or ventricular fibrillation or who are at very high risk for sudden cardiac death after MI should receive an automatic implantable cardioverter-defibrillator. There are no class I indications for the use of hormonal therapy in postmenopausal women after MI. Indications for coronary revascularization after MI in older individuals are prolongation of life and relief of unacceptable symptoms despite optimal medical management. |
3,627 | Remodeling of atrial dimensions and emptying function in canine models of atrial fibrillation. | Atrial tachycardia-induced remodeling (ATR) and ventricular tachypacing-induced heart failure (HF) create experimental substrates for atrial fibrillation (AF), and both have been reported to produce atrial dilation and hypocontractility. The relative importance of changes in atrial size and contractility in the two models is unknown. This study compared changes in atrial dimensions and emptying in ATR versus HF dog models and related them to AF promotion.</AbstractText>In ATR dogs (n=11), the right atrium (RA) was paced at 400/min for 42 days. In HF dogs (n=10), the right ventricle was paced at 240 bpm for 2 weeks, followed by 3 weeks at 220 bpm. Transthoracic echocardiography was performed at baseline and weekly thereafter. At a terminal electrophysiological study, RA effective refractory period (ERP) was recorded and AF induced repeatedly by atrial burst pacing to measure mean AF duration (DAF).</AbstractText>Left atrial (LA) systolic area increased by 10.0% in ATR versus 48.2% in HF dogs (P=0.008), with significant time-dependent changes in HF (P=0.0001), but not ATR (P=0.16). LA diastolic area increased over time in both groups (P=0.004, 0.0001 for ATR and HF respectively), but increases were much larger in CHF (80.2%) compared to ATR (24.2%, P=0.0002). Similar findings were obtained for RA. Fractional area shortening (FAS) decreased by 19.4% (ATR) versus 41.8% (HF, P=0.007) in LA and 13.7% (ATR) versus 33.7% (HF, P=0.03) in RA. RA ERP correlated with DAF in ATR dogs (r=-0.79, P<0.001), but not in HF dogs (r=0.20, P=NS). DAF and diastolic areas of RA and LA were highly correlated (r=0.71, 0.77; P<0.01 for each) in HF dogs, but not in ATR dogs (r=-0.18, 0.29; P=NS).</AbstractText>Remodeling of atrial size and emptying function is much greater in HF than in ATR. Whereas in ATR, electrophysiological remodeling is of prime importance in AF promotion, structural remodeling (as reflected in changes in atrial size and contraction) appears much more important in HF-induced AF.</AbstractText> |
3,628 | Left atrial systolic function in relation to electrical and mechanical remodeling in a canine model. | Rapid atrial activation causes electrical remodeling that promotes the occurrence and maintenance of atrial fibrillation. The aim of this research was to compare the relationship between mechanical remodeling and atrial electrophysiology. Eight dogs (beagles) were subjected to rapid atrial pacing (AP) at 400 beats/min for 16 days. After a complete recovery of electrical variables and left ventricular function evaluated by echocardiography, they underwent high-rate ventricular pacing (VP) at 240 beats/min of equal duration. In half of them, the study was started by VP and in the other half by AP. Left atrial systolic function was assessed by transesophageal echocardiography. Atrial effective refractory period (AERP) at a basic cycle length of 400 ms decreased significantly after either type of pacing (AP: 115 +/- 17 ms, VP: 136 +/- 22 ms) compared with baseline values (153 +/- 23 ms); the difference between tachycardias was significant too (p < 0.02). Significant increases (p < 0.05) in left atrial dimensions (LA-A) (AP: 2.41 +/- 0.23 cm ,VP: 2. 43 +/- 0. 34 cm vs. basal: 2. 16 +/- 0. 21 cm) indicated atrial dilatation after either type of pacing, the differences between two groups being insignificant. Atrial reversal pulmonary venous flow (AR velocity) decreased in AP (-0.13 +/- 0. 02 m/s) and VP (-0. 17 +/- 0. 04 m/s). The difference was highly significant as compared to basal values (-0.25 +/- 0.05 m/s) and also with respect to both tachycardias (p < 0.01). In both groups, atrial remodeling occurred in a relatively short period of time. The echocardiographic findings suggested that left atrial systolic function was significantly more disturbed in the AP group than in the VP group. Mechanical changes are an important substrate of electrical remodeling, yet the deterioration of electrical variables was more pronounced in AP than in VP. |
3,629 | [Atrial tachycardia, atrial flutter, atrial fibrillation: curative therapy by focal ablation in a pulmonary vein]. | We describe the case of a 50-year-old woman with the clinical diagnosis of cardiomyopathy associated with supraventricular tachycardia refractory to pharmacological treatment. The totally irregular tachyarrhythmia was the result of different episodes of atrial tachycardia, atrial flutter and atrial fibrillation that could be identified in the surface ECG. These findings and the patient's symptoms were all caused by a single focal tachycardia originating from the left upper pulmonary vein. Ablation of this focus represented a curative antiarrhythmic therapy also restoring a normalized ventricular function. Thus, an ablation of the AV node with consecutive pacemaker implantation could be prevented. |
3,630 | A new class of antiarrhythmic-defibrillatory agents. | Novel dibenzoazepine and 11-oxo-dibenzodiazepine derivatives are shown to be effective ventricular defibrillating drug candidates. They exhibit significant in vivo defibrillatory activity with no observed changes in ECG either before or after the VF event. These compounds also exhibit antifibrillatory activity by elevating the fibrillation threshold potential, all suggesting that such drugs could be used to treat VF either by themselves or together with electrical defibrillators. |
3,631 | Amiodarone in the new AHA guidelines for ventricular tachyarrhythmias. | To delineate amiodarone's role in the new American Heart Association guidelines for ventricular tachyarrhythmias, review the literature that supports the use of amiodarone in ventricular tachyarrhythmias, describe the pharmaceutical properties of amiodarone and elucidate their clinical implications, and discuss the dosing, preparation, and administration of amiodarone.</AbstractText>A search of MEDLINE (1966-October 2000) database and EMBASE Drugs and Pharmacology database (1980-October 2000) was performed. References from published articles and tertiary references were used to gather additional data.</AbstractText>All articles were screened, and pertinent studies were identified and evaluated.</AbstractText>Recent trials have demonstrated amiodarone's usefulness in the setting of ventricular tachyarrhythmias. Based on these investigations and contrary to past guidelines, amiodarone is included in the 2000 advanced cardiovascular life support guidelines as a possible agent for hemodynamically stable monomorphic ventricular tachycardia (VT), non-QT prolonged polymorphic VT, and ventricular fibrillation (VF)/pulseless VT. Although not specifically evaluated in the setting of hemodynamically stable monomorphic VT and non-QT prolonged polymorphic VT, investigations by the intravenous Amiodarone Multicenter Trial Group and other clinical trials make amiodarone an acceptable choice for these arrythmia categories. The results of the ARREST (Resuscitation of Refractory Sustained Ventricular Tachyarrhythmias) trial prove amiodarone to be the antiarrhythmic of choice for VF/pulseless VT.</AbstractText>Amiodarone is classified as a IIb therapeutic intervention for all three arrhythmia categories, which makes it an acceptable, safe, and useful agent with fair to good evidence to support its use. In addition, amiodarone requires careful preparation and delivery to achieve safe and effective outcomes.</AbstractText> |
3,632 | [Prevention of thromboembolism in non-rheumatic atrial fibrillation: an update]. | Randomized clinical trials have demonstrated the efficacy and safety of oral anticoagulants in the prevention of systemic thromboembolism in nonrheumatic atrial fibrillation. The benefit of this treatment is particularly evident in patients in whom atrial fibrillation is associated with a major risk factor for systemic thromboembolism (patients > 75 years of age, history of hypertension, previous left ventricular failure or previous systemic thromboembolism) or those in whom two minor risk factors are present (patients between 65 and 75 years of age, diabetes, ischemic heart disease). According to these recommendations, all the patients > 75 years of age with chronic or paroxysmal atrial fibrillation should receive oral anticoagulant treatment to maintain an INR between 2.0 and 3.0. However, as the risk of bleeding during oral anticoagulant treatment increases with age, the benefit/risk ratio should always be evaluated in elderly patients. Although high risk patients do not benefit from aspirin treatment, aspirin or other antiplatelet agents might be indicated in medium risk patients or in those in whom the risk of bleeding with oral anticoagulants is considered too high. New antithrombotic regimens will be tested in the near future. |
3,633 | A comparison of myocardial function after primary cardiac and primary asphyxial cardiac arrest. | Although myocardial dysfunction after resuscitation from ventricular fibrillation (VF) has been extensively investigated, less is known of the function of the myocardium after asphyxial cardiac arrest. The present experimental study was designed to compare postresuscitation left ventricular (LV) function after cardiac arrest caused by asphyxia with that of cardiac arrest induced by dysrhythmia. Four groups of Sprague-Dawley rats, which included eight animals in each group, were investigated. In the first two groups, cardiac arrest followed asphyxia produced by neuromuscular blockade with and without airway obstruction. In a third group, cardiac arrest was induced by electrical fibrillation of the ventricle. The fourth group represented animals in which the duration of asphyxial cardiac arrest was maintained for a time interval corresponding to that of the VF group. The fourth group received approximately the same number of electrical shocks as the third (VF) group. All animals were successfully resuscitated with precordial compression and mechanical ventilation. Postresuscitation measurements, including cardiac output, LV end-diastolic pressure (LVEDP), rate of pressure rise at LV pressure of 40 mm Hg (LV dP/dt40), and negative LV dP/dt, demonstrated decreased myocardial function in each group. No differences in cardiac function were observed between the animals with primary respiratory arrest whether or not the airway was obstructed. However, disproportionate and consistently greater impairment in myocardial function followed primary cardiac arrest due to VF when compared with equal duration of asphyxial cardiac arrest. We conclude that in this healthy animal model, asphyxial cardiac arrest resulted in significantly lesser impairment of postresuscitation myocardial function when compared with cardiac arrest caused by VF. |
3,634 | Vasopressin and shock. | Vasopressin (antidiuretic hormone) is emerging as a potentially major advance in the treatment of a variety of shock states. Increasing interest in the clinical use of vasopressin has resulted from the recognition of its importance in the endogenous response to shock and from advances in understanding of its mechanism of action. From animal models of shock, vasopressin has been shown to produce greater blood flow diversion from non-vital to vital organ beds (particularly the brain) than does adrenaline. Although vasopressin has similar direct actions to the catecholamines, it may uniquely also inhibit some of the pathologic vasodilator processes that occur in shock states. There is current interest in the use of vasopressin in the treatment of shock due to ventricular fibrillation, hypovolaemia, sepsis and cardiopulmonary bypass. This article reviews the physiology and pharmacology of vasopressin and all of the relevant animal and human clinical literature on its use in the treatment of shock following a MEDLINE (1966-2000) search. |
3,635 | Bystander cardiopulmonary resuscitation in prehospital cardiac arrest patients in Singapore. | The chain of survival emphasizes the importance of the four links associated with survival after cardiac arrest (CA). The involvement of laypersons has been increasing over the years. They have been contributing toward "early access," "early cardiopulmonary resuscitation" (CPR), and, of late, "early defibrillation," with the advent of automated external defibrillators (AEDs). Bystander CPR rates are difficult to assess due to the lack of formal documentation.</AbstractText>To assess the bystander CPR rate for CA patients brought to the emergency department (ED) of an urban, tertiary teaching hospital in the central part of Singapore, over a period of 12 months.</AbstractText>This was a retrospective cohort study carried out from May 1, 1999, to April 30, 2000. "Bystander CPR" refers to an attempt to perform basic CPR by someone who is not part of an organized emergency response system. In general, this refers to the person who witnesses the arrest.</AbstractText>There were 155 adult patients with CA who satisfied the inclusion criteria over the 12-month period. The median age was 62.1 +/- 6.4 years, and the majority of patients were brought in by ambulances (126, or 81.3%). There were 142 (91.6%) non-trauma and 13 (8.4%) trauma CAs. Most patients had the CA at home (96, or 61.9%), and the most common initial rhythm at presentation upon the arrival of the paramedics was ventricular fibrillation (VF) (50 patients, or 32.2%). The bystander CPR rate was 20.0% (i.e., 31 of the 155 patients). A total of 32 (20.6%) patients had return of spontaneous circulation (ROSC, defined as the return of a palpable pulse) and 31 (96.9%, or 31/32) of them were those who had some form of bystander CPR performed. Of these 31 who had bystander CPR, four (12.9%) were subsequently admitted to the intensive care unit (ICU), while among those who did not have bystander CPR, all had death pronounced in the ED. Of the four patients admitted to the ICU, three (3 of 4, or 75.0%; or 3 of 155 CA patients, or 1.9%) were subsequently discharged alive from the hospital.</AbstractText>The bystander CPR rate for prehospital CA was 20.0%. About 12.9% (4 patients) of those who had bystander CPR were admitted to the ICU, compared with none from the group that did not receive any form of bystander CPR. Three patients (1.9% of all prehospital CAs) were discharged alive from the hospital.</AbstractText> |
3,636 | A Utstein-style analysis of prognostic factors related to survival in out-of-hospital cardiac arrests in Akita-City, Japan. | To analyze the epidemiology of out-of-hospital cardiac arrests and to elucidate modifiable factors affecting survival, we conducted a prospective cohort study in a middle-sized urban city served by a single emergency medical service (EMS) system in which emergency medical technicians use an automated external defibrillator. Data were collected from out-of-hospital cardiac arrests occurring between 1 January, 1994 and 31 December, 1998 by applying the Utstein style. The main outcome measure was survival at 1 year after hospital discharge. The overall incidence of out-of-hospital cardiac arrest was 71.7/100 000 inhabitants/year. Resuscitations were attempted in 762 of 1118 patients with confirmed cardiac arrest. Of the 762 patients, 37 (4.86%) survived. The cause of cardiac arrest was presumed to be cardiac in 340 (44.6%). Of the 340 cardiac arrests, 180 (52.9%) were witnessed by bystanders. Ventricular fibrillation (VF) was recorded as an initial rhythm in 56 (31.1%) of the 180 patients, and cardiopulmonary resuscitation (CPR) was performed by bystanders in 89 (49.4%). The survival rate was 39.2% (22/56) when cardiac arrest was bystander-witnessed and of cardiac origin with VF as an initial rhythm. VF as an initial rhythm, age of the patients and intervals of call-to-first CPR attempt and collapse-to-arrival at patient's side were major factors relating to survival in the witnessed cardiac arrests of cardiac origin. The age, and gender of the patients, place of collapse and intervals of collapse-to-first CPR and collapse-to-arrival at patient's side were representative factors affecting the incidence of VF as an initial rhythm. The survival rate in Akita-City from bystander-witnessed cardiac arrests of cardiac origin with VF as an initial rhythm was comparable to those in other regions with advanced EMS systems. However, the incidence of VF as an initial rhythm is extremely low. Reduction of intervals of call (collapse)-to-first CPR attempt and collapse-to-arrival at patient's side or authorization of use of automated external defibrillator in basic life support may increase the incidence of VF as an initial rhythm and improve the survival from witnessed cardiac arrests with cardiac origin. |
3,637 | Anticoagulant (fluindione)-aspirin combination in patients with high-risk atrial fibrillation. A randomized trial (Fluindione, Fibrillation Auriculaire, Aspirin et Contraste Spontané; FFAACS). | A combination of low-dose aspirin with anticoagulants may provide better protection against thromboembolic events compared to anticoagulants alone in high-risk patients with atrial fibrillation.</AbstractText>Evaluation of the preventive efficacy against nonfatal thromboembolic events and vascular deaths of the combination of the oral anticoagulant fluindione and aspirin (100 mg) in patients with high-risk atrial fibrillation.</AbstractText>A multicenter, placebo-controlled, double-blind, randomized trial was conducted at 49 investigating centers in France. Atrial fibrillation patients with a previous thromboembolic event or older than 65 years and with either a history of hypertension, a recent episode of heart failure or decreased left ventricular function were included in the study. Patients were treated with fluindione plus placebo (i.e. anticoagulant alone) or fluindione plus aspirin (i.e. combination therapy), with an international normalized ratio target of between 2 and 2.6. The combined primary endpoint was stroke (ischemic or hemorrhagic), myocardial infarction, systemic arterial emboli or vascular death. The secondary endpoint was the incidence of hemorrhagic complications.</AbstractText>The 157 participants (average age 74 years; 52% women; 42% with paroxysmal atrial fibrillation) were followed for an average of 0.84 years. Three nonfatal thromboembolic events were observed (1 in the anticoagulation group, 2 in the combination group) and 6 patients died (3 in the anticoagulation group, 3 in the combination group), none of them from a thromboembolic complication. However, 3 deaths were secondary to severe hemorrhagic complications (1 in the anticoagulation group, 2 in the combination group). Nonfatal hemorrhagic complications occurred more often in the combination group (n = 10, 13.1%) compared to the anticoagulation group (n = 1, 1.2%) (p = 0.003).</AbstractText>The combination of aspirin with anticoagulant is associated with increased bleeding in elderly atrial fibrillation patients. The effect on thromboembolism and the overall balance of benefit to risk could not be accurately assessed in this study due to the limited number of ischemic events.</AbstractText>Copyright 2001 S. Karger AG, Basel</CopyrightInformation> |
3,638 | Reperfusion-induced Ins(1,4,5)P(3) generation and arrhythmogenesis require activation of the Na(+)/Ca(2+) exchanger. | Reperfusion of globally ischemic rat hearts causes rapid generation of inositol(1,4,5) trisphosphate [Ins(1,4,5)P(3)] and the development of arrhythmias, following stimulation of alpha(1)-adrenergic receptors by norepinephrine released from the cardiac sympathetic nerves. The heightened inositol phosphate response in reperfusion depends on the activation of the Na(+)/H(+) exchanger, which might reflect a central role for increased Ca(2+)following reverse mode activation of the Na(+)/Ca(2+) exchanger (NCX). Isolated, perfused rat hearts were subjected to 20 min ischemia followed by 2 min reperfusion and the content of Ins(1,4,5)P(3) measured by mass analysis or by anion-exchange high performance liquid chromatography (HPLC) following [(3)H]inositol labeling. Reperfusion caused generation of Ins(1,4,5)P(3) (1266+/-401 to 3387+/-256 cpm/g tissue, mean+/-s.e.m., n=6, P<0.01) and the development of arrhythmias. Inhibition of NCX either by reperfusion at low Ca(2+) (1133+/-173 cpm/g tissue, mean+/-s.e.m., n=6, P<0.01 relative to reperfusion control) or by adding 10 microm KB-R7943, an inhibitor of reverse mode Na(+)/Ca(2+) exchange, prevented the Ins(1,4,5)P(3) response (1151+/-243 cpm/g tissue, mean+/-s.e.m., n=6, P<0.01 relative to reperfusion control) and the development of ventricular fibrillation. Lower concentrations of KB-R7943 were less effective. Reverse mode activation of NCX is therefore required for the enhanced Ins(1,4,5)P(3) response in early reperfusion, and inhibitors of this transporter may be useful in the prevention of arrhythmias under such conditions. |
3,639 | Left ventricular mass regression after aortic valve replacement with CryoLife-O'Brien stentless aortic bioprosthesis. | Left ventricular (LV) hypertrophy has been shown adversely to affect LV function and late outcome after aortic valve replacement (AVR). The study aim was to assess the time course of LV mass regression (LVMR) after AVR with a CryoLife-O'Brien stentless bioprosthesis, and to identify factors affecting late reduction of myocardial hypertrophy.</AbstractText>In total, 113 patients (60 males, 73 females; mean age 70.9+/-6.5 years) were studied by echocardiography preoperatively, at discharge, at six and 12 months postoperatively, and yearly thereafter. LV diameter and thickness were measured using M-mode echocardiography; LV mass was calculated using the Devereux formula and indexed by body surface area (BSA).</AbstractText>LV end-systolic diameter, end-diastolic diameter, septal thickness and wall thickness decreased significantly after surgery (p <0.001). LV mass index (LVMI) was reduced by 16.6, 13.6, 10.1, 3.1, 3.3, 1.7, 2.6, and 1.8% at discharge and at 6 months and 1, 2, 3, 4, 5, and 6 years, respectively. Most LVMR occurred within the first year, with further (not significant) reductions at later examinations. Male sex (p = 0.002), arterial blood pressure > or =150 mmHg (p <0.001), LV ejection fraction (LVEF) < or =35% (p = 0.01), NYHA functional class > or = III (p = 0.01), atrial fibrillation (p <0.001), mean transvalvular gradient > or =40 mmHg (p = 0.001), and prevalent aortic incompetence (p <0.001) were factors influencing LVMR, independently of baseline effective orifice area and prosthesis size.</AbstractText>AVR with the CryoLife-O'Brien stentless prosthesis resulted in significant LVMR. These findings encourage the use of this bioprosthesis in appropriate patients.</AbstractText> |
3,640 | Predictors for atrial transport function after mini-maze operation. | Restoration of atrial transport function (ATF) is a major goal of the maze procedure. This prospective study was undertaken to evaluate predictors of left atrial transport function in patients undergoing a mini-variant of the maze III procedure 3 and 12 months postoperatively.</AbstractText>Mini-maze operation was performed in 72 patients with a mean age of 64 +/- 8.7 years during a 5-year period. Seventy of 72 (97%) had combined procedures. Clinical and electrophysiologic examination was carried out before surgery, and 3 and 12 months postoperatively.</AbstractText>Early mortality was 1.4% (1 of 72 patients) and late death occurred in 5.6% (4 of 71 patients). After 3 months, 54 of 68 (80%) patients showed sinus rhythm, and 48 of 60 (80%) after 12 months. ATF was restored in 87% (echocardiography) and 82% (magnetic resonance imaging) after 3 months, and in 86% (echocardiography) and 78% (magnetic resonance imaging) after 12 months. Independent predictors for ATF restoration after 12 months were better preoperative left ventricular function (p = 0.02), and smaller preoperative left atrial diameter (p = 0.005). Correlation between echocardiography and magnetic resonance imaging was 80% after 12 months.</AbstractText>Restoration of ATF after mini-maze procedure is achieved in over 80%. Independent predictors for ATF restoration are smaller preoperative left atrial diameter and better preoperative left ventricular ejection fraction.</AbstractText> |
3,641 | Effects of angiotensin II type 1 receptor antagonist (candesartan) in preventing fatal ventricular arrhythmias in dogs during acute myocardial ischemia and reperfusion. | Fatal arrhythmias may be prevented by long-term oral administration of angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 (AT 1 ) receptor antagonists. However, there have been no studies evaluating the electrophysiologic changes that occur with the acute administration of AT 1 receptor antagonists during acute myocardial ischemia and reperfusion. This study aimed to evaluate the ability of candesartan to prevent fatal arrhythmias during acute myocardial ischemia and reperfusion. The left anterior descending (LAD) coronary artery was ligated for 10 min and then reperfused for 10 min in 45 adult mongrel dogs. Candesartan (1 mg/kg) or saline was administered intravenously 10 min before ligation of the LAD coronary artery (candesartan group [n = 20] and control group [n = 25], respectively). Changes in ventricular effective refractory period (ERP) and intramyocardial conduction time (ICT) in the risk area were compared during LAD occlusion and reperfusion. Ischemia-induced shortening of ERP was inhibited in the candesartan group compared with the control. There was a 4.7 +/- 5.8% increase in ERP in the candesartan group, compared with a 11.5 +/- 6.3% shortening in the control group (p < 0.01). Prolongation of ICT was inhibited in the candesartan group compared with the control group during both ischemia and reperfusion (maximal prolongation of ICT: 0.1 +/- 3.0% vs. 37.7 +/- 9.6%, respectively; p < 0.01). Incidence of ventricular fibrillation was lower in the candesartan group than in the control group (25% [5/20] vs. 72% [18/25], respectively; p < 0.01). Candesartan suppresses changes in ERP and ICT during acute myocardial ischemia and reperfusion, suggesting that candesartan can prevent the development of fatal arrhythmias. |
3,642 | Incidence and prognostic significance of atrial fibrillation in acute myocardial infarction: the GISSI-3 data. | Atrial fibrillation is the most common supraventricular arrhythmia in patients with acute myocardial infarction. Recent advances in pharmacological treatment of myocardial infarction may have changed the impact of this arrhythmia.</AbstractText>To assess the incidence and prognosis of atrial fibrillation complicating myocardial infarction in a large population of patients receiving optimal treatment, including angiotensin converting enzyme (ACE) inhibitors.</AbstractText>Data were derived from the GISSI-3 trial, which included 17 944 patients within the first 24 hours after acute myocardial infarction. Atrial fibrillation was recorded during the hospital stay, and follow up visits were planned at six weeks and six months. Survival of the patients at four years was assessed through census offices.</AbstractText>The incidence of in-hospital atrial fibrillation or flutter was 7.8%. Atrial fibrillation was associated with indicators of a worse prognosis (age > 70 years, female sex, higher Killip class, previous myocardial infarction, treated hypertension, high systolic blood pressure at entry, insulin dependent diabetes, signs or symptoms of heart failure) and with some adverse clinical events (reinfarction, sustained ventricular tachycardia, ventricular fibrillation). After adjustment for other prognostic factors, atrial fibrillation remained an independent predictor of increased in-hospital mortality: 12.6% v 5%, adjusted relative risk (RR) 1.98, 95% confidence interval (CI) 1.67 to 2.34. Data on long term mortality (four years after acute myocardial infarction) confirmed the persistent negative influence of atrial fibrillation (RR 1.78, 95% CI 1.60 to 1.99).</AbstractText>Atrial fibrillation is an indicator of worse prognosis after acute myocardial infarction, both in the short term and in the long term, even in an unselected population.</AbstractText> |
3,643 | Electrophysiological effects of ibutilide in patients with accessory pathways. | Atrial fibrillation (AF) may cause life-threatening ventricular arrhythmias in patients with Wolff-Parkinson-White syndrome. We prospectively evaluated the effects of ibutilide on the conduction system in patients with accessory pathways (AP).</AbstractText>In part I, we gave ibutilide to 22 patients (18 men, 31+/-13 years of age) who had AF during electrophysiology study, including 6 pediatric patients </=18 years of age. Ibutilide terminated AF in 21 of 22 patients (95%) during or 8+/-5 minutes after infusion and prolonged the shortest preexcited R-R interval during AF. Successful ablation was performed in all patients. In part II, ibutilide was given to 18 patients (14 men, 28+/-21 years) to assess its effects on the AP and conduction system. Ibutilide prolonged the antegrade atrioventricular node effective refractory period (ERP) (from 252+/-60 to 303+/-70 ms; P<0.02). Ibutilide caused transient loss of the delta wave in 1 patient and abolished inducible tachycardia in 2 patients, although retrograde mapping still allowed for successful AP ablation. The antegrade AP ERP prolonged from 275+/-40 to 320+/-60 ms (P<0.01), as did the antegrade AP block cycle length; the retrograde AP ERP and block cycle length similarly prolonged with ibutilide. The relative and effective refractory period of the His-Purkinje system increased in 61% of patients after ibutilide. There were no adverse side effects.</AbstractText>We report the use of ibutilide in terminating AP-mediated AF, including the first report in the pediatric population. Ibutilide prolonged refractoriness of the atrioventricular node, His-Purkinje system, and AP.</AbstractText> |
3,644 | Are drugs and catheter ablation effective for treating ventricular arrhythmias in populations that cannot afford implantable cardioverter defibrillators? | Despite recent advances, ventricular arrhythmias continue to pose a therapeutic challenge, especially to the clinician in the developing world. Although the implantable cardioverter defibrillator (ICD) has improved survival in both primary and secondary prevention trials, it still remains a costly modality for the developing world. Even though certain subgroups stand to benefit unequivocally in survival from the ICD, there are others in whom this therapy may not offer a survival benefit over empiric antiarrhythmic drug therapy with amiodarone. The utility of optimized drug therapy (including either amiodarone or sotalol, b-blockers, and angiotensin-converting enzyme inhibitors) needs to be compared with the ICD in a randomized manner in these lower-risk patients with ventricular arrhythmias. The role of conventional catheter ablation techniques is mostly adjunctive to drugs and ICDs, although the newer mapping and ablation techniques may offer greater promise in the future. |
3,645 | Hematologic and chemical changes observed during and after cardiac arrest in a canine model--a pilot study. | To evaluate the effect of cardiac arrest and cardiopulmonary resuscitation (CPR) on blood chemistry in a canine model.</AbstractText>Evaluative canine animal study.</AbstractText>Animal laboratory accredited by the Association for Assessment and Accreditation of Laboratory Animals.</AbstractText>Twenty-six adult mongrel dogs.</AbstractText>The dogs underwent an episode of induced fibrillatory cardiac arrest for 3 minutes followed by 10 minutes of standard CPR. Blood samples were taken at baseline (before cardiac arrest), after 10 minutes of ventricular fibrillation, and 10 minutes after successful resuscitation for determination of blood chemistries and hematologic parameters.</AbstractText>Glucose, blood urea nitrogen, serum creatinine, sodium, potassium, chloride, calcium, phosphorus, uric acid, alkaline phosphatase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, protein, albumin, cholesterol, triglycerides, iron, white blood cell count, red blood cell count, and hematocrit were measured. Significant changes (p<0.05) in values obtained during CPR versus baseline values were noted for all laboratory parameters except blood urea nitrogen, chloride, and alkaline phosphatase. Eighteen dogs achieved return of spontaneous circulation (ROSC); their laboratory values were obtained after CPR. Significant changes (p<0.05) after ROSC compared with baseline were noted for all laboratory values except chloride, blood urea nitrogen, uric acid, alkaline phosphatase, glucose, potassium, calcium, triglycerides, iron, red blood cell count, and hematocrit.</AbstractText>Results indicate that significant changes in blood chemistries and hematologic parameters occur during and after CPR. Clinicians should note these normal laboratory parameter changes when interpreting laboratory data in patients who experience cardiac arrest.</AbstractText> |
3,646 | Does simultaneous antegrade and retrograde cardioplegia improve functional recovery and myocardial homeostasis? | The purpose of our research was to evaluate the functional recovery and homeostasis of myocardium during simultaneous continuous retrograde and antegrade cardioplegia versus continuous retrograde cardioplegia.</AbstractText>Forty patients who underwent elective coronary artery bypass grafting (CABG) were prospectively assigned to two clinically matched groups and analyzed in respect to cardioplegia protocol. Group I consisted of 24 patients who received continuous retrograde blood cardioplegia; Group II consisted of 16 patients who received simultaneous continuous ante- and retrograde cardioplegia. Hydrogen ion release, carbon dioxide, lactate concentration oxygen content, and oxygen extraction were measured from coronary sinus effluent and from the arterial line before and after cross-clamping of the aorta. Median changes of these parameters were reported. Cardiac output was measured and left and right ventricle stroke works were calculated. Incidence of low cardiac output, ventricular fibrillation, raised cardiac enzymes, and ischemic changes on electrocardiogram (ECG) were noted.</AbstractText>In the simultaneous group, oxygen content and oxygen extraction recovered well after cross-clamping. The same parameters did not recover to the same extent in the retrograde group. These changes were notable between groups. Hydrogen ion, carbon dioxide, and lactate releases were comparable between groups. Trend toward better recovery of left ventricle stroke work index was encountered in the simultaneous group.</AbstractText>Viability of myocardium measured with oxygen utilization and functional recovery is better preserved with simultaneous antegrade and retrograde cardioplegia. However, there is no difference in anaerobic metabolism markers. Thus simultaneous ante- and retrograde cardioplegia is probably advantageous over retrograde alone.</AbstractText> |
3,647 | Magnetocardiographic mapping of QRS fragmentation in patients with a history of malignant tachyarrhythmias. | The identification of patients at increased risk for ventricular tachycardia or ventricular fibrillation (VT/VF) and sudden cardiac death has consequences for therapeutic options and thus may reduce mortality in patients with coronary artery disease (CAD).</AbstractText>We hypothesized that the intra-QRS fragmentation in magnetocardiographic recordings is increased in patients with CAD and with a history of VT/VF.</AbstractText>Multichannel magnetocardiography (MCG) was carried out in 34 healthy controls, 42 patients with CAD without a history of VT/VF, and 43 patients with CAD and with a history of VT/VF. The intra-QRS fragmentation was quantified by a new fragmentation score. Its spatial distribution was investigated using two-dimensional (2-D) contour maps according to the sensor position of the 49-channel magnetogradiometer.</AbstractText>Patients with CAD and with a history of VT/VF had significantly increased QRS fragmentation compared with patients with CAD without VT/VF or controls (72.9+/-37.5, 48.5+/-14.3, and 42.5+/-7.8, respectively: p <0.05). The area of high fragmentation in 2-D contour maps was twice as large in patients with than in those without a history of VT/VF (represented by the number of MCG channels with high fragmentation: 26.3+/-15.5 vs. 12.4+/-9.9, p<0.0001). Patients prone to VT/VF could be identified with a sensitivity of 64% and a specificity of 90%.</AbstractText>In patients with CAD and with a history of VT/VF, intra-QRS fragmentation is increased and the area of high fragmentation in 2-D contour maps is enlarged. These findings may be helpful in identifying patients with CAD at risk for malignant tachyarrhythmias.</AbstractText> |
3,648 | A new detection algorithm for implantable cardioverter defibrillator. | One of the most important subsystems of implantable cardioverter defibrillator (ICD) is the sensing stage, since it determines the sensitivity and specificity of the device to detect the heart rate and the underlying arrhythmia. This paper aims to investigate a new detection algorithm for ICD, which operates fully automatically. The algorithm ARGUS was implemented as a computer model and tested with intracardiac electrograms recorded (band-pass: 0.05 to 500 Hz; sampling rate: 1-4 kHz) under different rhythm condition like sinus rhythm (n = 18), atrial tachycardia (n = 16), and ventricular tachycardia as well as fibrillation (n = 139) during electrophysiological tests or ICD implantation. The results of the tests were visually inspected on a beat-to-beat basis. In total 31,934 events were classified by the algorithm (18,758 as long intervals (LI) with cycle length > 300 ms; 13,176 as short intervals (SI)). 195 out of the 13,176 SI and 572 out of 18,758 LI were incorrectly classified (SI: 1.48%; LI: 3.05%). In conclusion the new algorithm yield high sensitivity (99.9%) and specificity (97.0%) as known from conventional ICD algorithms but need no manual adjustments. |
3,649 | [An unconscious patients with ascending aortic aneurysm accompanied by aortic regurgitation successfully treated by emergency operation after cardiopulmonary resuscitation]. | A-37-year-old woman in shock condition was transferred to our hospital after cardiopulmonary resuscitation for ventricular fibrillation. She was unconscious and suspected of suffering ischemic brain damage, with pathologic reflexes and weak brain stem reflexes. Brain CT scan showed cerebral edema without hemorrhage or infarction and an electroencephalograph revealed slow alpha-theta waves. Chest CT scan and echocardiogram showed ascending aortic aneurysm with sever aortic regurgitation. An emergent operation was performed for progression of heart failure. There were no distortion or dilatation of the sinus of Valsalva and annuloaortic ectasia and aortic valve leaflets were almost normal. We considered that the aortic valve dysfunction was cause by dilatation of the sinotubular junction. Ascending aortic and aortic valve replacement were carried out to shorten cardiopulmonary bypass time and to prevent the progression of brain damage. Mild hypothermia was employed as a neuroprotective procedure for three days after surgery. The patient's neurological symptoms, which were right hemiparesis, facial apraxia and motor aphasia, improved and she was discharged from the hospital on foot without any neurological complications on the 47th postoperative day and returned to work after two months. |
3,650 | Eustachian valve endocarditis caused by Streptococcus viridans. | A 76-year-old man was admitted for ethanol detoxification. He was found to be in atrial fibrillation with a rapid ventricular response that was refractory to electrical and chemical cardioversion attempts. The patient subsequently developed respiratory distress. A transesophageal echocardiogram revealed a vegetation attached to the eustachian valve and blood cultures grew Streptococcus viridans. After treatment with appropriate antibiotics, the patient converted to sinus rhythm with sotalol hydrochloride, and the eustachian valve vegetation resolved. This is the first reported case of eustachian valve endocarditis caused by S viridans. |
3,651 | Intramyocardial hematoma mimicking abnormal left ventricular trabeculation. | Intramyocardial hematoma may present as a tumor or pseudoaneurysm on echocardiography. A 68-year-old man was admitted with a subacute posterior wall infarction complicated by ventricular fibrillation. Echocardiography showed isolated left ventricular abnormal trabeculations, a finding suggesting an associated skeletal muscle disorder, in the lateral wall. At cardiac surgery, performed 6 weeks later because of severe 3-vessel disease, an intramyocardial hematoma of the lateral wall was excised, and myocardial and skeletal muscle biopsies were taken, which showed neither isolated left ventricular abnormal trabeculations nor skeletal muscle disorder. Postoperatively, echocardiography revealed no abnormal trabeculations. |
3,652 | Compensatory responses of left atrial conduit flow to atrial fibrillation with acute myocardial infarction in a canine model. | The aim of this study was to examine the interaction of acute atrial fibrillation (Af) and acute myocardial infarction (AMI) on left atrial (LA) and left ventricular (LV) filling in atrioventricular (A-V) sequential paced, open chest, anesthetized dogs. Left atrial conduit function was determined from pulmonary venous flow (PVF) and detailed analysis of early diastolic flow with the use of micromanometers and transmitral Doppler echocardiography. We studied 8 dogs with regular ventricular rates to avoid the confounding effect of ventricular arrhythmia in Af. In the control stage, Af increased the diastolic PVF volume to the left atrium compared with that during regular A-V pacing (from 0.58 +/- 0.11 mL/beat to 0.70 +/- 0.13 mL/beat, P <.05), as a compensatory response to the impaired systolic PVF volume (from 0.56 +/- 0.12 mL/beat to 0.41 +/- 0.11 mL/beat, P <.05). As a result, cardiac output was maintained. However, in the AMI stage, Af decreased cardiac output (from 0.95 +/- 0.32 L/min to 0.80 +/- 0.23 L/min, P <.05 versus AMI with A-V pacing), and decreased diastolic PVF volume (from 0.46 +/- 0.13 mL/beat to 0.33 +/- 0.14 mL/beat, P <.05 versus AMI with A-V pacing). These changes were associated with a prolonged LV isovolumic pressure decay rate. Our study demonstrates that Af does not affect cardiac output in the setting of normal LV function at a controlled ventricular rate because enhanced LA conduit flow compensates for impaired LA reservoir function. In contrast, in the setting of AMI, the compensatory response to Af is attenuated because of abnormal LV relaxation, resulting in a decrease in cardiac output. |
3,653 | Effect of amiodarone on atrial fibrillation after coronary artery bypass surgery. | Atrial fibrillation occurs in 10% 40% of patients undergoing coronary artery bypass grafting. This study investigates whether prophylactic Amiodarone use reduces the rate of atrial fibrillation post myocardial revascularisation.</AbstractText>In a prospective study conducted at the Cardiothoracic Center over a 6 month period, 192 patients were randomized to either Amiodarone or placebo. The Amiodarone group received Amiodarone infusion followed by oral Amiodarone on a decreasing dose for a total period of 6 weeks. The placebo group were started on an infusion of dextrose 5% solution and then maintained on a matched regimen of placebo tablets for a corresponding period of time.</AbstractText>Of the 100 patients recruited for the Amiodarone arm of the study, 12 were excluded for a variety of reasons detailed in the discussion with atrial fibrillation occurring in 28 (a rate of 32%). Of the 92 controls, 32 developed atrial fibrillation (a rate of 35%). There were no significant differences between the groups. The maximum ventricular rate during atrial fibrillation however, was significantly slower in the Amiodarone group (108+/-18) compared to (136+/-22) P<0.05. Moreover, there were no significant differences in the mortality rates between the 2 groups; a rate of 3% (3 of 88) in the Amiodarone group as opposed to 3% (3 of 92) in the controls.</AbstractText>In this study prophylactic Amiodarone did not reduce the rate of atrial fibrillation post coronary artery bypass surgery. However, it reduced the maximum ventricular rate. Amiodarone had no effect on mortality post coronary artery bypass.</AbstractText> |
3,654 | Clinical performance of a specific algorithm to reconfirm self-terminating ventricular arrhythmias in current implantable cardioverter-defibrillators. | Inappropriate shock therapy is a frequent problem in patients with implantable cardioverter-defibrillators (ICDs), caused mostly by supraventricular rhythms. Self-terminating ventricular arrhythmias (STVAs), however, may also lead to inappropriate shock discharges even in ICDs with abortive shock capabilities. The aim of this study was to evaluate the clinical performance of a specific ventricular tachycardia/ventricular fibrillation (VT/VF) reconfirmation algorithm implemented in current ICD devices from Medtronic to prevent inappropriate shock discharges due to STVAs. A total of 161 STVA episodes were documented in 59 of 150 patients (39%) within a mean follow-up of 30 +/- 20 months and resulted in 25 inappropriate shock discharges in 15 of 150 patients (10%) despite activation of the reconfirmation algorithm. The first synchronization interval of the algorithm was met in 92% of STVA episodes with and even 38% of STVA episodes without shock delivery. A reduced incidence of inappropriate shocks due to STVAs was found with tachycardia/fibrillation detection intervals (TDI/FDI) programmed to shorter cycle lengths < or =280 ms or the use of the first 2 cycles after the end of charging to be considered for reconfirmation only. Thus, inappropriate shocks due to STVAs still occur in 10% of patients with ICDs despite activation of a specific VT/VF reconfirmation algorithm, and are mainly caused by meeting the first synchronization interval that therefore should be shortened in cycle length. Moreover, to reduce the likelihood of inappropriate shocks, the VF reconfirmation algorithm should be optimized by basing the synchronization intervals exclusively on the FDI with short cycle lengths or using the first 2 cycles for reconfirmation only. |
3,655 | [Stroke of cardioembolic origin in Chagas disease]. | American trypanosomiasis, Chagas disease is caused by Trypanosoma cruzi. Between 10% and 30% of infected persons develop the chronic form, with predominance of the cardiac and gastrointestinal forms. Chagas myocardiopathy leads to congestive heart failure, dysrhythmias and thromboembolic phenomena, and may cause strokes.</AbstractText>We report two patients, a 57 year old woman and a 52 year old man, carriers of the chronic cardiac form of Chagas disease, with cardioembolic strokes. In both persons, serology was positive for Chagas disease (indirect hemagglutination and indirect immunofluorescence). The causes of atherothrombotic stroke were ruled out on carotid and transcranial Doppler studies.</AbstractText>The woman had previously had an infarct of the left middle cerebral artery. She was admitted with a stroke involving the vertebrobasilar territory. On Holter studies there was second degree atrioventricular block and the electrocardiogram showed severe dilated myocardiopathy. On magnetic resonance studies there was an old left temporoparietal infarct and recent ischaemia of the pons and cerebral peduncle. She was anticoagulated and a pacemaker implanted. The man had a right middle cerebral artery infarct. His electrocardiogram showed atrial fibrillation and left anterosuperior block. The echocardiogram showed left ventricular dysfunction and concentric ventricular hypertrophy.</AbstractText>The chronic cardiac form of Chagas disease should be included in the differential diagnosis of stroke of cardioembolic origin both in endemic areas and in countries to which persons exposed to infection during the early years of life emigrate.</AbstractText> |
3,656 | Quinidine induced electrocardiographic normalization in two patients with Brugada syndrome. | Two patients with Brugada syndrome are presented. The ECGs showed right precordial J waves and ST-segment elevation. Patient 1 was resuscitated from nocturnal ventricular fibrillation, patient 2 was asymptomatic. In only patient 1, flecainide was infused causing monomorphic "malignant" ventricular extrasystoles (R on T), demonstrating the deleterious effect of Class IC antiarrhythmic drugs in Brugada syndrome. However, administration of the Class Ia antiarrhythmic drug quinidine caused normalization of the ECG in both patients. Based on in vitro experiments, agents that reduce the magnitude of Ito-mediated phase 1 have been suggested to normalize ST-segment elevation in Brugada syndrome. This is the first clinical report of such a quinidine induced ECG normalization. |
3,657 | Combined cardiomyopathy and skeletal myopathy: a variant with atrial fibrillation and ventricular tachycardia. | This article describes a family characterized by combined cardiomyopathy and nonspecific skeletal myopathy who present in the third to fifth decades with cardiac manifestations but earlier have evidence of subtle skeletal muscle dysfunction. They differ from previously defined syndromes and potentially represent a different genetic expression or mutation. Cardiomyopathy presents with atrial arrhythmias including AF and atrial flutter. Life-threatening ventricular tachyarrhythmias occur next with onset of ventricular dysfunction. Electrophysiological study revealed sustained monomorphic VT. Affected family members benefitted from an ICD and progression to congestive heart failure (CHF) occurred late. Skeletal myopathy continues with marked progressive muscle weakness and inability to ambulate without assistance. Genetic analysis is currently ongoing. Neurological evaluation in all three family members revealed nonspecific myopathy affecting the psoas and iliopsoas muscles. Atrophy and wasting of the facial and temporalis muscles were common. Skeletal muscle biopsy revealed myofiber atrophy consistent with myopathy. |
3,658 | Response of atrial fibrillatory activity to carotid sinus massage in patients with atrial fibrillation. | In some cases carotid sinus massage (CSM) may induce AF, whereas it may terminate AF in others. The purpose of this study was to investigate the influence of CSM on atrial fibrillatory frequency using spectral analysis of the surface ECG. Continuous ECG recordings were made in 19 patients (12 men, 7 women, mean age 61 +/- 11 years) with AF. Unilateral CSM was performed in the standard fashion to one randomized bifurcation of the carotid artery at a time. Ventricular rate and fibrillatory frequency were assessed in 30-second ECG segments at baseline and during CSM. The frequency content of the fibrillatory baseline was quantified using digital signal processing (filtering, subtraction of averaged QRST complexes, and Fourier transformation). CSM resulted in a relative change in fibrillatory frequency of 4.5 +/- 3.9% (range 0%-13%). In 8 (42%) patients an increase in fibrillatory frequency was found (6.4 +/- 0.5 vs 6.8 +/- 0.5 Hz, P = 0.012). In 9 (47%) patients a decrease in fibrillatory frequency occurred (6.5 +/- 0.8 vs 6.1 +/- 0.8 Hz, P = 0.008) without AF termination. The remaining two patients showed no change in fibrillatory frequency. CSM on the contralateral side after 2 minutes produced fibrillatory frequency changes in the same direction in all patients with a good reproducibility in its magnitude (r = 0.59, P = 0.05). Calcium channel blockers were more frequently used (78% vs 25%, P = 0.044) in patients with a decrease in fibrillatory frequency compared to patients with a frequency increase. There were no significant changes in ventricular rate during CSM. In conclusion, two different responses of atrial fibrillatory frequency to CSM were found. This might explain why CSM may facilitate AF induction in some cases and AF termination in others. Calcium channel blocker treatment may prevent an increase in fibrillatory frequency provoked by CSM suggesting a blunted electrical remodeling process. |
3,659 | Correlation between defibrillation shock outcome and coherence in electrocardiograms. | Cycle periods in ECG during VF are correlated with periods of reentrant activation. The ECGs recorded from different locations on the thorax were contributed to from electrical activations within the heart in approximately inverse proportion of their distance from the recording sites. Similarity in cycle periods between ECGs recorded from two locations, therefore, can be used as an index of spatiotemporal similarity in the rate of activation. In the present study coherence was used, which is a mathematical function that measures the degree of similarity that two signals exhibit at specific cycle periods, to test if spatiotemporal similarity in cycle periods between pairs of orthogonal ECGs was correlated with defibrillation shock outcome. The authors estimated time-varying coherence from orthogonal ECGs during 10 seconds of electrically induced VF, which was terminated with a defibrillation shock with a 50% probability of successful outcome. Defibrillation shocks were delivered between a coil electrode placed at the right ventricular apex and a subdermal patch electrode. Time-varying coherencies between pairs of ECGs were estimated using an adaptive least mean square algorithm. Time-coherence surfaces were integrated within a frequency region centered at the dominant frequency. Data were collected from ten dogs during 206 (48%) successful and 221 (52%) unsuccessful trials. The results showed that coherencies between the sagittal-transverse pair were 10%-15% higher (P < 0.05) for successful than unsuccessful trials. The correlation between coherence and defibrillation outcome suggests that more defibrillation shocks occurred when the degree of spatial similarity in the rate of activations was higher terminated VF, than those that occurred at other times. These results are consistent with a hypothesis, recently proposed by others, that more uniform activation within regions of the heart that receive low potential gradients during shock may increase the probability of successful defibrillation. |
3,660 | Bidirectional defibrillation using implantable defibrillators: a prospective randomized comparison between pectoral and abdominal active generators. | The objective of this study was to compare the effects of active abdominal and pectoral generator positions on DFTs in a bidirectional tripolar ICD system. Twenty-five consecutive patients had ICD systems implanted under general anesthesia. A transvenous single lead bipolar defibrillation system and an active 57-cc test emulator in the abdominal and pectoral positions were used in the same patient. A randomized, alternating step-down protocol was used starting at 15 J with 3-J decrements until failure. The mean implantation time was 114 +/- 23 minutes, the mean arrhythmia duration was 14.5 +/- 1.5 seconds, and the mean recovery time was 5.4 +/- 1.1 minutes. The mean DFTs in the abdominal and pectoral positions were 10.9 +/- 5.1 and 9.7 +/- 5.2 J, respectively (NS), the mean intraindividual DFT difference (abdominal minus pectoral) was -0.89 +/- 4.15 J (range -9.5 to 8 J). The 95% confidence interval showed a -2.60 to +0.82 J mean difference (NS). The DFT was < 15 J in 72% and 88% of the patients and the defibrillation impedance was 41 +/- 3 and 44 +/- 3 omega, abdominal versus pectoral positions. There was no difference in DFT between active abdominal and pectoral generator bidirectional tripolar defibrillation. The pectoral position may be considered the primary option, but in cases of high DFTs the abdominal site should be considered an alternative to adding a subcutaneous patch. In some patients, the anatomy may favor an abdominal position. Possible differences in the long-term functionality on the leads are not yet well known and need to be further evaluated. |
3,661 | Enhanced detection criteria in implantable cardioverter defibrillators: sensitivity and specificity of the stability algorithm at different heart rates. | The lack of specificity in the detection of ventricular tachyarrhythmias remains a major clinical problem in the therapy with ICDs. The stability criterion has been shown to be useful in discriminating ventricular tachyarrhythmias characterized by a small variation in cycle lengths from AF with rapid ventricular response presenting a higher degree of variability of RR intervals. But RR variability decreases with increasing heart rate during AF. Therefore, the aim of the study was to determine if the sensitivity and specificity of the STABILITY algorithm for spontaneous tachyarrhythmias is related to ventricular rate. Forty-two patients who had received an ICD (CPI Ventak Mini I, II, III or Ventak AV) were enrolled in the study. Two hundred ninety-eight episodes of AF with rapid ventricular response and 817 episodes of ventricular tachyarrhythmias were analyzed. Sensitivity and specificity in the detection of ventricular tachyarrhythmias were calculated at different heart rates. When a stability value of 30 ms was programmed the result was a sensitivity of 82.7% and a specificity of 91.4% in the detection of slow ventricular tachyarrhythmias (heart rate < 150 beats/min). When faster ventricular tachyarrhythmias with rates between 150 and 169 beats/min (170-189 beats/min) were analyzed, a stability value of 30 ms provided a sensitivity of 94.5% (94.7%) and a specificity of 76.5% (54.0%). For arrhythmia episodes > or = 190 beats/min, the same stability value resulted in a sensitivity of 78.2% and a specificity of 41.0%. Even when other stability values were taken into consideration, no acceptable sensitivity/specificity values could be obtained in this subgroup. RR variability decreases with increasing heart rate during AF while RR variability remains almost constant at different cycle lengths during ventricular tachyarrhythmias. Thus, acceptable performance of the STABILITY algorithm appears to be limited to ventricular rate zones < 170 beats/min. |
3,662 | Quadruple pads approach for external cardioversion of atrial fibrillation. | This study examined the alternative of transthoracic quadruple pads shock delivery of two simultaneous 360-J shocks to convert refractory AF in patients failing standard external cardioversion. Forty-six patients (mean age 58 +/- 11 years, 23 men) with chronic AF (duration 14 +/- 17 months, range 1-60 months) were included. The left atrial diameter was 47 +/- 7 mm. The left ventricular ejection fraction was 59 +/- 11%. Antiarrhythmic drugs had failed to convert 44 (96%) of these patients. All patients underwent conventional external transthoracic cardioversion with pads applied in the antero-apical position using energy settings of 200 and 360 J, consecutively. In all patients who failed conventional cardioversion, quadruple pads were applied. Quadruple pads consisted of four pads, two in the antero-posterior position and two in a second apex-posterior position. Standard cardioversion to sinus rhythm was successful in 19 (41%) patients after use of a single 200-J shock and an additional 8 (17%) after a single 360-J shock. The total success rate was 58% after conventional cardioversion. The quadruple pads were successful in 14 (74%) of the remaining 19 patients. Four of the five patients who failed the quadruple pads approach subsequently also failed internal cardioversion. Thus, the cardioversion success rate was increased from 48% using the conventional approach to 89% using the quadruple pads approach. Quadruple pads external cardioversion is highly effective in converting chronic AF refractory to standard shock protocols to sinus rhythm. Moreover, the failure of the quadruple pads approach seems to predict poor response to internal cardioversion. |
3,663 | Radiofrequency energy modification of the atrioventricular junction in patients with atrial fibrillation: modes of ventricular response under autonomic blockade and long-term effect. | The short- and long-term effect of radiofrequency (RF) modification of the AV junction on ventricular rate and left ventricular function and the different types of ventricular response during energy application under autonomic nervous blockade were assessed in 28 patients with medically refractory atrial fibrillation. During the successful RF application, ventricular rate slowed progressively (type I response, ten patients) or accelerated at first and then slowed (type II response, 11 patients). Type II response was associated with a more anterior ablation site compared to Type I response. A primary successful outcome was achieved in 21 patients. Inadvertent complete AV block developed in three patients, while in four patients AV nodal ablation was performed after an unsuccessful modification attempt. During 6-month follow-up, the ventricular rate was adequately controlled in only four patients. Among the 16 patients with a recurrence of uncontrolled AF were all 10 patients with type I response and 6 of 11 patients with type II response. One patient died suddenly 10 weeks after the procedure. |
3,664 | Severe hypothermia with cardiac arrest: complete neurologic recovery in a 4-year-old child. | A 4-year-old girl was lost for 17 hours in a snowstorm. Upon discovery, her core temperature was 72 degrees F (22 degrees C). While undergoing endotracheal intubation in the emergency department, she experienced sudden ventricular fibrillation and cardiac arrest. Closed chest cardiopulmonary resuscitation (CPR) was instituted, and standard rewarming measures were begun. Despite this, neither core temperature, nor the patient's arrhythmia, changed. An infraumbilical "mini-laparotomy" incision was made, with placement of a large silicone peritoneal dialysis catheter into the abdomen. This was then connected to a rapid infuser device, with the delivery of 1L of warmed, normal saline every 90 seconds. The core temperature reached 29 degrees C in 15 minutes, and a palpable pulse was detected. Lavage was continued until core temperature reached 34 degrees C, at which time transport to the pediatric intensive care unit was arranged. She was extubated the next day and discharged home, on the fourth hospital day, with apparent complete neurologic recovery. This is the first report of the successful use of rapid high-volume peritoneal lavage for the treatment of accidental severe hypothermia in a pediatric patient. |
3,665 | Prevention of ventricular fibrillation during acute myocardial ischemia: control of free fatty acids. | Fatal ventricular fibrillation is a common complication of acute coronary syndromes. Effective preventive measures are not available. Immediate restriction of free fatty acid availability should optimize ischemic myocardial metabolism, reduce ventricular vulnerability, and increase glucose utilization. Rapid inhibition of lipoprotein lipase activity will achieve this. The clinical effects of antilipolytic treatment require further study. |
3,666 | Should an abnormal serum potassium concentration be considered a correctable cause of cardiac arrest? | According to American Heart Association/American College of Cardiology Practice Guidelines, electrolyte abnormalities, including abnormal serum potassium concentrations, are considered a correctable cause of a life-threatening ventricular arrhythmia. Ventricular defibrillator therapy in this situation is a class III indication, and thought to be ineffective and perhaps harmful, although there are minimal data to support this recommendation. The steady-state serum potassium concentration frequently changes during a cardiac arrest. Additionally, the vast majority of cardiac arrest patients have structural heart disease and are commonly treated with a variety of medications that can alter the serum potassium concentration. In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a correctable cause of an electrolyte imbalance were excluded from study participation but were followed in the AVID registry. Similar outcomes were observed among patients in the AVID registry and the main trial. Spironolactone therapy in patients with congestive heart failure decreases all-cause mortality and sudden and nonsudden cardiac death. In a preliminary study of 169 patients with an episode of a sustained ventricular arrhythmia treated with an implantable defibrillator, freedom from appropriate defibrillator therapy was 18% after five years. The probability of appropriate defibrillator therapy was independent of the initial serum potassium concentration. For these reasons, our current clinical practice is to use an implantable defibrillator to treat an initial episode of sustained ventricular tachycardia or ventricular fibrillation that occurs in a patient with structural heart disease and an abnormal serum potassium concentration. |
3,667 | [Comparison of clinical and electrophysiologic characteristics of patients with occult and manifest atrioventricular accessory pathway]. | It is current opinion that concealed and manifest accessory pathways (APs) are indistinguishable with respect to their location and contribution to orthodromic reciprocating tachycardias. The aim of this study was to compare clinical and electrophysiological characteristics of two groups of patients.</AbstractText>Between January 1999 and June 2000, 42 consecutive patients underwent radiofrequency catheter ablation for paroxysmal atrioventricular reciprocating tachycardia attributable to a concealed AP. Their clinical and electrophysiological characteristics were compared with a group of 48 consecutive patients with manifest AP and supraventricular tachyarrhythmias.</AbstractText>There were no differences regarding gender, the prevalence of heart disease and the age of onset of symptomatic tachycardias between the two groups. Compared to those with a manifest AP, the patients presenting with a tachyarrhythmia due to a concealed AP were older (48 +/- 15 vs 40 +/- 16 years, p < 0.05) and had a longer history of tachyarrhythmias (22 +/- 16 vs 13 +/- 13 years, p < 0.05). Atrial fibrillation was more frequent in patients with a manifest AP than in patients with a concealed AP (50 vs 9.5% respectively, p = 0.02). Atrioventricular reciprocating tachycardia was a cause of more hospitalizations (76 vs 35%, p = 0.01) and episodes of pre-syncope (47 vs 22%, p < 0.05) in the group of patients with a concealed AP. The anatomical site of concealed and manifest APs was significantly different: concealed APs were more frequently localized in the left side (93% left, 7% right), while manifest APs were seen in the left side in 64% of cases, in the right side in 29% and in the posteroseptal left + right region in 7% of cases. The retrograde electrophysiological properties and the inducibility of other types of reentrant arrhythmias were similar. Catheter ablation was similarly successful regardless of whether the AP was concealed or manifest, the rates of success being 91 and 88% respectively at the first attempt and with a similar number of energy applications (7 +/- 7 vs 10 +/- 9, p = NS). At a second attempt, the procedure was successful in 100 and 98% of cases respectively. Periprocedural complications occurred in 5% of patients with a concealed (1 ventricular fibrillation, 1 cerebral transient ischemic attack) and in 8% of patients with a manifest AP (2 pericardial effusion, 1 transient atrioventricular block, 1 anginal attack with spontaneous recovery) (p = NS). Complications occurred only for left-sided APs and were independent of the approach (transseptal or retrograde). Relapse of AP conduction was more frequent in the group of patients with a manifest than in those with a concealed AP (12 vs 5%), though not significantly. There were no late complications.</AbstractText>Those patients presenting with a tachyarrhythmia due to a concealed AP, compared to those with a manifest AP, were older and had a longer history of tachyarrhythmia. Atrial fibrillation was more frequent in patients with manifest AP. Atrioventricular reciprocating tachycardia episodes were longer-lasting and caused more hospitalizations and more frequently pre-syncope in the group of patients with a concealed AP. Almost all concealed APs were localized in the left side. The retrograde electrophysiological properties were similar. The results of radiofrequency catheter ablation were comparable in both groups.</AbstractText> |
3,668 | Effect of clinical risk stratification on cost-effectiveness of the implantable cardioverter-defibrillator: the Canadian implantable defibrillator study. | Three randomized clinical trials showed that implantable cardioverter-defibrillators (ICDs) reduce the risk of death in survivors of ventricular tachyarrhythmias, but the cost per year of life gained is high. A substudy of the Canadian Implantable Defibrillator Study (CIDS) showed that 3 clinical factors, age >/=70 years, left ventricular ejection fraction </=35%, and New York Heart Association class III, predicted the risk of death and benefit from the ICD. We estimated the extent to which selecting patients for ICD therapy based on these risk factors makes ICD therapy more economically attractive.</AbstractText>Patients in CIDS were grouped according to whether they had >/=2 of 3 risk factors. Incremental cost-effectiveness of ICD therapy was computed as the ratio of the difference in mean cost to the difference in life expectancy between the 2 groups. Over 6.3 years, the mean cost per patient in the ICD group was Canadian (C) $87 715 versus $38 600 in the amiodarone group (C$1 approximately US$0.67). Life expectancy for the ICD group was 4.58 years versus 4.35 years for amiodarone, for an incremental cost-effectiveness of ICD therapy of C$213 543 per life-year gained. The cost per life-year gained in patients with >/=2 factors was C$65 195, compared with C$916 659 with <2 risk factors.</AbstractText>The cost-effectiveness of ICD therapy varies by patient risk factor status. The use of ICD therapy in patients who have >/=2 risk factors of age >/=70 years, left ventricular ejection fraction </=35%, and NYHA class III is C$65 195 to gain a year of life.</AbstractText> |
3,669 | Dispatcher assistance and automated external defibrillator performance among elders. | Automated external defibrillators (AEDs) provide an opportunity to improve survival in out-of-hospital, ventricular fibrillation (VF) cardiac arrest by enabling laypersons not trained in rhythm recognition to deliver lifesaving therapy. The potential role of emergency dispatchers in the layperson use of AEDs is uncertain. This study was performed to examine whether dispatcher telephone assistance affected AED skill performance during a simulated VF cardiac arrest among a cohort of older adults. The hypothesis was that dispatcher assistance would increase the proportion who were able to correctly deliver a shock, but might require additional time.</AbstractText>One hundred fifty community-dwelling persons aged 58-84 years were recruited from eight senior centers in King County, Washington. All participants had received AED training approximately six months previously. For this study, the participants were randomized to AED operation with or without dispatcher assistance during a simulated VF cardiac arrest. The proportions who successfully delivered a shock and the time intervals from collapse to shock were compared between the two groups.</AbstractText>The participants who received dispatcher assistance were more likely to correctly deliver a shock with the AED during the simulated VF cardiac arrest (91% vs 68%, p = 0.001). Among those who were able to deliver a shock, the participants who received dispatcher assistance required a longer time interval from collapse to shock [median (25th, 75th percentile) = 193 seconds (165, 225) for dispatcher assistance, and 148 seconds (138, 166) for no dispatcher assistance, p = 0.001].</AbstractText>Among older laypersons previously trained in AED operation, dispatcher assistance may increase the proportion who can successfully deliver a shock during a VF cardiac arrest.</AbstractText> |
3,670 | Post-resuscitative hypothermic bypass reduces ischemic brain injury in swine. | Increasing human and laboratory evidence suggests that post-resuscitative brain hypothermia reduces the pathologic consequences of brain ischemia. Using a swine model of prolonged cardiac arrest, this investigation sought to determine whether unilateral hypothermic carotid bypass was capable of inducing selective brain hypothermia and reducing neurohistologic damage.</AbstractText>Ventricular fibrillation was induced in common swine (n = 12). After 20 minutes of cardiopulmonary arrest (without ventilatory support or cardiopulmonary resuscitation), systemic extracorporeal bypass was instituted to restore coronary and cerebral perfusion, followed by restoration of normal sinus rhythm. Animals randomized to the normal brain temperature (NBT) cohort received mechanical ventilation and intravenous fluids for 24 hours. The selective brain hypothermia (SBH) cohort received 12 hours of femoral/carotid bypass at 32 degrees C. The bypass temperature was then increased one degree per hour until reaching 37 degrees C and continued at this temperature until completion of the protocol (24 hours). Histopathologic damage was evaluated in two areas of the hippocampus.</AbstractText>Normal sinus rhythm was restored in all animals after the systemic (femoral/femoral) bypass was initiated. Nasal temperature (surrogate measure of brain temperature) remained higher than 37.0 degrees C throughout the 24-hour recovery period in the NBT animals. In the SBH cohort, right nasal temperature dropped to the mild hypothermic range (<34 degrees C) two hours after institution of femoral/carotid bypass. This was maintained throughout the 12-hour cooling period without hemodynamic compromise. There was a significant improvement in the neurohistology scores in the CA1 region of the hippocampus of the SBH treated animals as compared with those of the NBT cohort.</AbstractText>Post-resuscitative selective brain hypothermia reduced regional ischemic brain damage in swine with prolonged ventricular fibrillation.</AbstractText> |
3,671 | [The risk of direct current countershock]. | Direct current cardioversion (DCC) is a procedure commonly used to restore the sinus rhythm in patients with supraventricular and ventricular arrhythmias. Its safety, regarding the use of electric current, is still a matter of controversy and debate. The patients with atrial fibrillation/flutter, supraventricular or ventricular tachycardia represent a broad spectrum of clinical conditions and it is difficult to draw the conclusions. The high success rate of DCC in restoring the sinus rhythm, may be partly responsible for enhancing and revealing proarrhythmic properties of antiarrhythmic drugs. The deaths described as a complications of DCC were mainly due to the proarrhythmia and less common to the progression of the pathologic process. The embolic, arrhythmic and anesthetic complications of DCC can be prevented if the known recommendations of performing the DCC are followed. The authors review critically the literature data about the complications of the procedure and come to the conclusion of safety of DCC. |
3,672 | [Tachycardia-induced cardiomyopathy]. | Dilated cardiomyopathy induces circulatory insufficiency with poor prognosis. Persistent tachyarrhythmias may be the cause of this disease. At particular high risk for heart damage and insufficiency are young people and children. The group of most dangerous arrhythmias consist of: incessant tachycardia in patients with preexcitation syndrome and supraventricular tachyarrhythmias (atrial flutter and fibrillation, ectopic atrial tachycardia) with high rate of ventricles. The result of arrhythmias is dilatation of the heart and thinness of ventricular walls with hemodynamic disorders. The effective therapy of arrhythmias--ablation of the accessory pathway in patients with pre-excitation syndrome or reversion to sinus rhythm (pharmacological or electric cardioversion) in patients with atrial fibrillation and flutter, often leads to normalisation of heart ejection function and diameter. Therefore it exist important question: is dilated cardiomyopathy the cause or consequence of tachyarrhythmias? Causative antiarrhythmic therapy in these second cases gives a possibility to improve the prognosis in patients with such a disease. |
3,673 | [Association between mitral annulus calcification and atherosclerosis]. | Mitral annulus calcification (MAC) is best diagnosed by transthoracic echocardiography. MAC is associated with known atherosclerotic risk factors such as diabetes mellitus, hypertension and hypercholesterolemia. It is also known from the literature that patients with MAC have higher prevalence of left atrial and left ventricular enlargement, hypertrophic cardiomyopathy, atrial fibrillation, aortic valve calcification and stenosis, various cardiac conduction defects, bacterial endocarditis, cardiovascular events and stroke, though the etiological basis is unknown. Pathological studies from the 80's present a theory that MAC is a form of atherosclerosis. During the past few years we conducted a few clinical studies in order to test this theory and to examine the association between MAC and known atherosclerotic phenomena. We found higher prevalence of aortic atheroma in patients with MAC, especially complex atheroma, and we also found a continuous correlation between the MAC and atheroma thickness. We also noted that MAC patients have a higher prevalence of carotid artery stenosis, coronary artery stenosis, peripheral artery stenosis and higher levels of anti beta 2-Glycoprotein I antibodies in patients with MAC thickness equal or greater than 5 mm. These studies support the theory that MAC is a form of atherosclerosis and define a group of patients with higher prevalence of atherosclerotic disease in multiple blood vessels. |
3,674 | Experiences with iohexol and iodixanol during cardioangiography in an unselected patient population. | To compare the frequency of adverse events after cardioangiography with iohexol and iodixanol in an unselected patient population with special regard to previously defined "risk patients": age> or =65 years, severe coronary artery disease, unstable angina pectoris and left ventricular dysfunction.</AbstractText>A total of 1020 patients referred to cardioangiography were included in this open, prospective cross-sectional study, comparing iodixanol (320 mgI/ml) and iohexol (350 mgI/ml). Adverse events were recorded and the patients answered a questionnaire.</AbstractText>Cardiac adverse events (CAE) i.e., angina pectoris, arrhythmia and dyspnea within 24 h of examination were reported by 9% of patients receiving iohexol and by 7% receiving iodixanol. Two cases of ventricular fibrillation occurred, both after iohexol. The proportion of CAE was 11% for patients> or =65 years receiving iohexol and 7% in younger patients. For patients receiving iodixanol the proportion was 7%, in both age groups. Patients with severe coronary disease had more CAE than less ill patients in both CM groups. The proportion of unstable patients with CAE was 18% in the iohexol group and 12% in the iodixanol group. Left ventricular dysfunction was not related to CAE.</AbstractText>Iodixanol could be advantageous in patients with unstable angina.</AbstractText> |
3,675 | [Familial junctional ectopic tachycardia: clinical and pathological findings]. | We describe two brothers with a neonatal diagnosis of junctional ectopic tachycardia. The first brother presented hydrops fetalis secondary to narrow QRS tachycardia at a rate of 230-300 beats/min with atrioventricular dissociation. Although the ventricular rate was controlled with intravenous amiodarone the baby died a few hours after initiation of this treatment from ventricular fibrillation and electromechanical dissociation. Histological examination of the conduction system showed diffuse hemorrhage and necrosis of the atrioventricular node and His' bundle. The second brother presented fetal distress and polyhydramnios and the postnatal electrocardiogram revealed junctional ectopic tachycardia at a rate of 170 beats/min alternating with sinus rhythm, which was controlled without treatment. |
3,676 | Effect of interatrial block on left atrial function. | Interatrial block produces prolonged P-waves due to conduction delay mainly in the Bachmann bundle, the most direct route from right to left atrium. It is prevalent in patients over age 60 with its main clinical significance its association with eventual atrial fibrillation and/or flutter. Having demonstrated a mean delay in the onset of active left ventricular filling of 37 msec, we defined the electromechanical abnormality further by measuring left atrial volume at key points in the atrial cycle to produce 10 measurements of left atrial function. Compared to the normal left atrium, interatrial block is correlated with a large, poorly contractile left atrium with a delayed and markedly reduced contribution to left ventricular filling and the kinetic energy with which atrial systole propels blood. |
3,677 | [Congestive heart failure caused by the thyroid stimulating hormone(TSH) secreting pituitary adenoma: report of two cases]. | A 42-year-old man and a 31-year-old man with congestive heart failure caused by the thyroid stimulating hormone(TSH) secreting pituitary adenoma were reported. Heart failure was improved after transsphenoidal resection of the pituitary adenoma in each patient. The syndrome of inappropriate secretion of TSH causes hyperthyroidism. Thyroid hormone acts directly on cardiac muscle to increase the stroke volume. Hyperthyroidism itself reduces the peripheral vascular resistance and an elevated basal metabolism which is the basic physiologic change in hyperthyroidism dilates small vessels and reduces vascular resistance. The reduced vascular resistance contributes to increase stroke volume. Thyroid hormone also acts directly on the cardiac pacemakers to be apt to cause tachycardiac atrial fibrillation. These mechanical changes in hyperthyroidism increase not only the cardiac output but also the venous return. The increased blood volume and the shortened ventricular filling time due to tachycardia result in congestive heart failure. TSH secreting pituitary adenoma is a rare tumor, however heart failure is common disease. TSH secreting pituitary adenoma should be taken into consideration in patients with heart failure. The presented cases were very enlightening to understand the relation between brain tumor and heart disease. |
3,678 | [Attempted CPR in nursing homes - life-saving at the end of life?]. | We studied the course and success rate of cardiopulmonary resuscitation (CPR) attempted on nursing home residents by a physician-staffed pre-hospital advanced cardiac life support (ACLS) team.</AbstractText>Ambulance records of nursing home residents from Goettingen/Germany who had a cardiac arrest were examined retrospectively.</AbstractText>During a seven-year period (1992 - 1998) the ACLS team was called to 71 residents (mean age 81.8 years) who sustained cardiac arrest. In 25 patients no CPR was attempted: 20 were pronounced dead by the arriving emergency physician, though only in 7 patients obvious clinical signs of death were present. Five patients suffered from a continuous deterioration of their health status and the ACLS team arrived after the process of dying had already started. No CPR attempt was initiated. The ACLS team performed CPR on 46 nursing home residents. In 33 patients (72 % of CPR attempts) no return of spontaneous circulation (ROSC) was achieved. In three patients (6%) palpable pulse returned only transiently. Ten patients (22 %) who showed ROSC were transported to the hospital. Six patients died within 24 hours after having been admitted to the hospital, two patients within the next 8 days. Two patients survived to hospital discharge. The first was a 79-year old woman who returned to the nursing home after three weeks and survived severely mentally disabled another five days. The second was an 83-year-old man who was hospitalised for 20 days, returned in a persistent vegetative state to the nursing home and died 10 months later. A comparison of the arrest characteristics demonstrated that in patients with successful CPR there was a higher incidence of a witnessed collapse, bystander CPR, ventricular fibrillation and cardiac aetiology of arrest.</AbstractText>In a high rate (35 %) the ACLS team with the emergency physician at the scene withheld CPR efforts in nursing home residents. Even if CPR was initiated, the benefits were very limited with only two patients (4,3 %) surviving severely disabled to hospital discharge.</AbstractText> |
3,679 | Use of intraoperative transesophageal echocardiography to predict atrial fibrillation after coronary artery bypass grafting. | Postoperative atrial fibrillation in coronary artery bypass graft surgery occurs in 10-40% of patients. It is associated with a significant degree of morbidity and results in prolonged lengths of stay in both the intensive care unit and hospital.</AbstractText>The authors prospectively evaluated patients undergoing coronary artery bypass with detailed transesophageal echocardiography examinations conducted before and after cardiopulmonary bypass to study whether risk factors for atrial fibrillation could be identified. Demographic and surgical parameters were also included in the analysis. Selected variables were subjected to univariate and subsequent multivariate analyses to test for their independent or joint influence on atrial fibrillation.</AbstractText>Seventy-nine patients had assessable transesophageal echocardiography examinations. Significant univariate predictors of atrial fibrillation included advanced age (P = 0.002), pre-cardiopulmonary bypass left atrial appendage area (P = 0.04), and post-cardiopulmonary bypass left upper pulmonary vein systole/diastole velocity ratio (P = 0.03). When these three factors were considered together in a multiple logistic regression analysis, left upper pulmonary vein systole/diastole velocity ratio was a significant predictor (P < 0.05), as was the joint effect of age plus pre-cardiopulmonary bypass left atrial appendage area (P = 0.005). The probability of developing atrial fibrillation for the combination of age = 75 yr, post-cardiopulmonary bypass left upper pulmonary vein systole/diastole velocity ratio = 0.5, and left atrial appendage area = 4.0 cm was 0.83 (95% confidence interval, 0.51-0.96).</AbstractText>Early identification of patients at risk for postoperative atrial fibrillation may be feasible using the parameters identified in this study.</AbstractText> |
3,680 | [Aorta-left ventricular relationship evaluated by Doppler echocardiography and ambulatory arterial prsesure monitoring]. | Arterial distensibility is one of the components of afterload. Arterial distensibility, left ventricular (LV) mass and LV function are closely linked. The aim of this study is to describe the relations between LV mass LV function and arterial distensibility evaluated by echography Doppler (échography Doppler) and ambulatory monitoring pressure. Sixty-two patients with or without cardiac disease were prospectively enrolled excepted those with atrial fibrillation, left bundle branch block pace maker, or valvulopathy. Echography Doppler study collected stroke volume, LV diameters and wall thickness, ejection time (ET) and preejection time (PET); were calculated ejection fraction (EF), systolic pressure/systolic diameter ratio, LV mass index (LVMI), relative wall thickness ratio (e/r). AMP collected usual pressure datas and QKd, time interval between QECG and diastolic Korotkoff sound, instantaneous, over 24 h (i, 24 h), and for a pressure of 100 mm Hg and a heart rate of 60 bpm (QKd 100-60).</AbstractText>QKd 24 h was correlated with LVMI (r = 0.40, p = 0.006) and e/r (r = 0.32, p = 0.028). QKdi was correlated with EF (p < 0.001, r = 0.65), with systolic pressure/systolic diameter ratio (p < 0.001, r = 0.75), and with ET/PET (r = 0.56, p < 0.001). When PET was withdrawn from QKd, no correlation exist between QKd-PET and LV function index, excepted QKd-PET versus systolic pressure/systolic diameter (r = 0.46, p = 0.005).</AbstractText>QKd is not only an arterial distensibility index but also a LV function index, because PET is included in it. Echography Doppler and AMP are available and common tools to study the aorta/LV relationship.</AbstractText> |
3,681 | [Doppler echocardiographic study of arterial distensibility. Comparison with ambulatory arterial pressure monitoring]. | Echocardiography Doppler (ED) is a common tool in hypertension to assess left ventricular (LV) mass or LV function. Echography doppler is also available to assess some arterial distensibility (AD) indexes, but it is less frequently used. The aim of this study is to compare AD indexes obtained from échographie doppler with timing of Korotkoff sound (QKd interval), obtained from ambulatory blood pressure monitoring (APM). Sixty-two patients with or without cardiac diseases were prospectively enrolled, except those with left bundle branch, atrial fibrillation or pacemaker. Echography doppler study collected timing of abdominal pulse (QtAA), interval time between Q ECG and the foot of doppler wave velocity in abdominal aorta pulse wave velocity (PWV) between two points of descending thoracic aorta; and Stroke index. APM study collected simultaneous usual pressure indexes (systolic diastolic, pulse pressure) instantaneous and over 24 h, and QKd interval times between Q ECG and diastolic Korotkoff sound instantaneous and over 24 h. Absolute AD Index (Burton index) was defined as Stroke index/pulse pressure. QtAA intra observer variability was the coefficient of variation (mean/SD). QtAA inter observer variability was QtAA assessments by two observers.</AbstractText>QtAA was correlated with QKdi (r = 0.78; p < 0.001) and QKd24 h (r = 0.64; p < 0.001). PWV was correlated with QKdi (r = 0.35; p = 0.009), but not with QKd24 h (r = 0.17; p = 0.24, NS). Burton index was correlated with QKdi (r = 0.48; p < 0.001), and QKd24 h (r = 0.53; p < 0.001).</AbstractText>Echography doppler may provide some arterial distensibility indexes. Among these indexes, QtAA is easy to obtain and well correlated with QKd. However, further studies are needed to assess normal and pathological values.</AbstractText> |
3,682 | Follow-up of patients with unexplained syncope and inducible ventricular tachyarrhythmias: analysis of the AVID registry and an AVID substudy. Antiarrhythmics Versus Implantable Defibrillators. | A prospective registry and substudy were conducted in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study to clarify the prognosis and recurrent event rate, risk factors, and impact of implantable cardioverter defibrillator (ICD) therapy in patients with unexplained syncope, structural heart disease, and inducible ventricular tachyarrhythmias.</AbstractText>Included in the AVID registry were patients from all participating sites who had "out of hospital syncope with structural heart disease and EP-inducible VT/VF with symptoms." In addition, 13 collaborating sites provided more in-depth clinical and electrophysiologic data as part of a formal prospective substudy. Patients in the substudy were followed by local investigators for recurrent arrhythmic events and mortality. Registry patients were tracked for fatal outcomes by the National Death Index. A total of 429 patients with syncope were entered in the AVID registry, of whom 80 participated in the substudy. Of the substudy patients, 21 patients (26%) had inducible polymorphic ventricular tachycardia/ventricular fibrillation (VT/VF), 11 patients (14%) had sustained monomorphic VT <200 beats/min, and 48 patients (60%) had sustained monomorphic VT > or = 200 beats/min. The ICD was used as sole therapy in 75% of the syncope substudy patients (and with antiarrhythmic drug in an additional 9%) and in 59% of the syncope registry patients. Survival rates at 1 and 3 years were 93% and 74% for the substudy patients and 90% and 74% for the registry patients, respectively. Survival of the syncope substudy patients (predominantly treated by ICD) was similar to the VT patients treated by ICD and superior to the VT patients treated by an antiarrhythmic drug (P = 0.05) in the randomized main trial. Mortality events in the substudy were marginally predicted by ejection fraction (P = 0.06) but not by electrophysiologic study-induced arrhythmia. The significant predictor of increased mortality in the registry was age (P = 0.003) and of reduced mortality was treatment with ICD (P = 0.006).</AbstractText>The results of these analyses support the role of the ICD as primary antiarrhythmic therapy in patients with unexplained syncope, structural heart disease, and inducible VT/VF at electrophysiologic study.</AbstractText> |
3,683 | Relationship between rehospitalization and future death in patients treated for potentially lethal arrhythmia. | It is generally considered that death is the only appropriate endpoint to evaluate interventions for preventing death; however, this belief may be based on the previous use of inappropriate or inadequate surrogates for death. The aim of this study was to evaluate whether rehospitalization following implementation of an intervention is a reasonable surrogate for death.</AbstractText>The time from discharge following intervention to rehospitalization was evaluated for 997 patients discharged after baseline hospitalization in the Antiarrhythmics Versus Implantable Defibrillators Trial. The relationship between rehospitalization for various reasons and subsequent death was compared in the two treatment arms to assess the adequacy of rehospitalization as a surrogate for death. Included were rehospitalization for: any reason, a cardiac problem, a noncardiac problem, new or worsened congestive heart failure (CHF), an acute coronary syndrome, and a cardiac procedure. For all of the reasons except cardiac procedure, rehospitalization was associated with a substantially increased hazard for subsequent death. Rehospitalization for new or worsened CHF was most closely (that is, temporally) related to subsequent death and was the only reason for rehospitalization, which fully explained the treatment effect of implantable cardiac defibrillators compared with antiarrhythmic drugs on death.</AbstractText>Rehospitalization is a significant risk factor for subsequent death. However, only rehospitalization for new or worsened CHF appears to be a potential surrogate for death in the setting of antiarrhythmic interventions.</AbstractText> |
3,684 | Excessive charge time delaying ventricular tachycardia therapy. | A 70-year-old man with a single-chamber implantable cardioverter defibrillator (ICD) placed for ventricular tachycardia presented with syncope. He was found to have ventricular flutter/fibrillation with capacitor charge time in excess of 1 minute before defibrillation. The excessive charge time was secondary to ICD capacitor malfunction. The generator was explanted and replaced, and the patient recovered uneventfully. |
3,685 | Modulation of QT interval by cardiac sympathetic nerve sprouting and the mechanisms of ventricular arrhythmia in a canine model of sudden cardiac death. | We previously reported that there is a high incidence of sudden cardiac death (SCD) in dogs with myocardial infarction (MI), complete AV block (CAVB), and nerve growth factor (NGF) infusion to the left stellate ganglion (LSG). Whether or not QT interval prolongation underlines the mechanism of SCD was unclear.</AbstractText>We analyzed QT intervals in three groups of dogs. All dogs had CAVB and MI. The LSG group (n = 9) and right stellate ganglion (RSG) group (n = 6) received NGF infusion via the osmotic pumps over a 5-week period to LSG and RSG, respectively. The control group (n = 6) received no NGF. The dogs either died suddenly or were sacrificed within 2 to 3 months after MI. Heart rhythm and QT and RR intervals were monitored using implantable cardioverter defibrillator ECG recordings. There was a time-dependent increase of QTc intervals in the LSG group and a time-dependent decrease of QTc intervals in the RSG group. At the end of NGF infusion, QTc intervals in the LSG group (408 +/- 41 msec) were significantly longer than those in the control (350 +/- 41 msec; P < 0.05) and RSG groups (294 +/- 23 msec; P < 0.01). In the LSG group, 4 of 9 dogs died of SCD. There was no SCD in either the RSG or control group. Immunocytochemical staining showed NGF infusion to LSG and RSG resulted in left and right ventricular sympathetic nerve sprouting and hyperinnervation, respectively.</AbstractText>NGF infusion to the LSG in dogs with MI and CAVB resulted in increased QT interval and incidence of ventricular tachycardia, ventricular fibrillation, and SCD, whereas NGF infusion to the RSG shortened QT interval and reduced the incidence of ventricular tachycardia. These findings indicate that QT interval prolongation is causally related to the occurrence of ventricular arrhythmia in dogs with nerve sprouting, MI, and CAVB.</AbstractText> |
3,686 | Effects of linear, irrigated-tip radiofrequency ablation in porcine healed anterior infarction. | Radiofrequency (RF) catheter ablation for ventricular tachycardia (VT) in healed infarction is modestly successful. More extensive, anatomically based procedures and irrigated RF delivery may improve outcome. However, limited data exist regarding the characteristics of irrigated RF lesions in infarcted myocardium. This study addresses this shortcoming.</AbstractText>Linear lesions were created at the medial border of a healed anterior infarct in eight pigs using irrigated RF energy guided by sinus rhythm electroanatomic voltage mapping and intracardiac echocardiography (ICE). Lesion morphology and effects on ventricular function were assessed with ICE imaging and pathologic analysis (n = 5). The response to programmed stimulation also was determined before and after linear lesions (n = 6). A mean of 9.4 +/- 1.3 RF applications created linear lesions 37.0 +/- 10.6 mm long, 5 to 12 mm wide, and 4 to 8 mm deep. Thrombus formation was not observed. Lesion delivery resulted acutely in increased local wall thickness at the RF site (26.9% +/- 27.5%; P < 0.0001) and transient systolic dysfunction in adjacent normal myocardium (fractional shortening -38% +/- 34%; P < 0.01). Uniform sustained VT (cycle length 232 +/- 41 msec) was induced in 4 of 6 pigs before ablation, but sustained VT could not be induced afterward.</AbstractText>Irrigated RF energy produced relatively large lesions in infarcted myocardium without thrombus formation. Changes in tissue thickness and echo density observed with ICE verify irrigated RF lesion delivery. Temporary left ventricular dysfunction is consistently observed in the normal myocardium adjacent to the linear lesion.</AbstractText> |
3,687 | Effects of azimilide, a new class III antiarrhythmic drug, on reentrant circuits causing ventricular tachycardia and fibrillation in a canine model of myocardial infarction. | Azimilide blocks the slow (I(Ks)) and fast (I(Kr)) components of the delayed rectifier potassium channel. It also has blocking effects on sodium (I(Na)) and calcium currents (I(CaL)). Its effects on reentrant circuits in infarct border zones causing ventricular tachyarrhythmias are unknown.</AbstractText>Activation in reentrant circuits causing sustained ventricular tachycardia (SVT) and the initial polymorphic tachycardia that leads to ventricular fibrillation (VF) was mapped in the epicardial border zone (EBZ) of 4-day-old canine infarcts. Azimilide prolonged the effective refractory period (ERP) in both normal myocardium and EBZ, but reverse use-dependence in EBZ was prominent. Azimilide abolished SVT initiation by programmed electrical stimulation by prolonging the ERP at the site of stimulation either in normal or EBZ, preventing the occurrence of early premature impulses and the formation of lines of block in the EBZ necessary for formation of reentrant circuits. Azimilide prevented VF initiation by programmed electrical stimulation by causing conduction block of reentrant impulses in the EBZ during the initial beats of rapid polymorphic ventricular tachycardia, despite the reverse use-dependent effects on ERP.</AbstractText>Azimilide has antiarrhythmic effects to prevent reentry causing SVT and VF in a canine infarct model.</AbstractText> |
3,688 | Resting ECG abnormalities among asymptomatic Arab men and comparison with other ethnic populations. | The aim of this study was to detect the frequency of the resting electrocardiogram (ECG) abnormalities among asymptomatic Arab men in Saudi Arabia, since no similar studies had been conducted in this ethnic population. The ECG tracings of 314 men (mean age 44.2 years) who attended a health clinic in Abha, Southern Saudi Arabia, were analyzed according to the definitions of the major ECG textbooks and the Minnesota code. Abnormal ECG findings were encountered in 99 men (31.5%); 39 (12.4%) had non-specific changes, while 60 (19.1%) had potentiallysignificantabnormalities. Serious abnormalities, such as ischemic changes, left ventricular hypertrophy, and atrial fibrillation were seen in only 22 subjects (7%) and were associated with hypertension and an age greater than 40 years. On the other hand, early repolarization, the most frequent abnormality encountered, and Wolf-Parkinson-White syndrome (WPW) were mostly prevalent among young subjects. The significance of these ECG abnormalities with regard to long-term morbidity and mortality in asymptomatic subjects should be considered in relation to the age of the person and the presence of any underlying cardiovascular disease. |
3,689 | Gap junction blockers decrease defibrillation thresholds without changes in ventricular refractoriness in isolated rabbit hearts. | The maintenance and termination of reentry arrhythmias are determined by tissue properties such as refractoriness and conduction velocity. Although the effects of Na(+) and K(+) channel block on electrophysiological properties and defibrillation threshold (DFT) have been studied, little is known about the effect of gap junction blockers on defibrillation and tissue electrophysiological properties.</AbstractText>Triplicate DFTs (volts) were obtained before and 15 minutes after 4 micromol/L 16-doxyl-stearic acid (16-DSA, n=8), 1 mmol/L 1-heptanol (n=12) (both gap junction blockers), 3 microg/mL lidocaine (a sodium channel blocker) (n=8), and respective controls (n=27) in isolated perfused rabbit hearts. DFT decreased after 16-DSA (23+/-14%, P<0.01) and 1-heptanol (21+/-16%, P<0.01) but increased after lidocaine (26+/-28%, P<0.05). Ventricular fibrillation cycle length (VFCL) and QRS duration increased after all 3 agents, by 36+/-19% and 44+/-16% (16-DSA), 87+/-42% and 49+/-15% (heptanol), and 57+/-20% and 43+/-26% (lidocaine), respectively (all P<0.01). Spatially averaged temporal VFCL dispersion decreased significantly after all 3 agents, by 47+/-42% (16-DSA, P<0.05), 74+/-19% (1-heptanol, P<0.01), and 82+/-13% (lidocaine, P<0.01), respectively. Ventricular effective refractory period and monophasic action potential duration at 90% repolarization were unchanged after 16-DSA and 1-heptanol (P=NS) but increased after lidocaine (16+/-13%, P<0.01, and 6+/-5%, P=NS, respectively). There were no significant changes in DFT or any other electrophysiological variable in control hearts.</AbstractText>Electrical uncoupling by 16-DSA and 1-heptanol significantly lowers DFT and dispersion of VFCL without altering refractoriness; lidocaine, at doses resulting in similar slowing of conduction, increases DFT.</AbstractText> |
3,690 | Pharmacologic conversion of atrial fibrillation: a systematic review of available evidence. | This report reviews the efficacy of currently available antiarrhythmic agents for conversion of atrial fibrilation (AF) to normal sinus rhythm (NSR). A systematic search of literature in the English language was done on computerized databases, such as MEDLINE, EMBASE, and Current Contents, in reference lists, by manual searching, and in contact with expert informants. Published studies involving humans that described the use of antiarrhythmic therapy for conversion of AF to NSR were considered and only studies that examined the use of agents currently available in the United States were included. Studies exclusively describing antiarrhythmic therapy for conversion of postsurgical AF were excluded. The methodology and results of each trial were assessed and attempts were made to acquire additional information from investigators when needed. Assessment of methodological quality was incorporated into a levels-of-evidence scheme. Eighty-eight trials were included, of which 34 (39%) included a placebo group (level I data). We found in recent-onset AF of less than 7 days, intravenous (i.v.) procainamide, high-dose i.v. or high-dose combination i.v. and oral amiodarone, oral quinidine, oral flecainide, oral propafenone, and high-dose oral amiodarone are more effective than placebo for converting AF to NSR. In recent-onset AF of less than 90 days, i.v. ibutilide is more effective than placebo and i.v. procainamide. In chronic AF, oral dofetilide converts AF to NSR within 72 hours, and oral propafenone and amiodarone are effective after 30 days of therapy. We conclude than for conversion of recent-onset AF of less than 7 days, procainamide may be considered a preferred i.v. agent and propafenone a preferred oral agent. For conversion of recent-onset AF of longer duration (less than 90 days), i.v. ibutilide may be considered a preferred agent. For patients with chronic AF and left ventricular dysfunction, direct current cardioversion is the preferred conversion method. Larger, well-designed randomized controlled trials with clinically important endpoints in specific populations of AF patients are needed. |
3,691 | Enhanced in vivo and in vitro contractile responses to beta(2)-adrenergic receptor stimulation in dogs susceptible to lethal arrhythmias. | The response to beta-adrenergic receptor (beta-AR) stimulation was evaluated in both isolated cardiomyocytes (video edge detection) and the intact animal (echocardiography) in dogs either susceptible (S) or resistant (R) to ventricular fibrillation induced by a 2-min coronary occlusion during the last minute of exercise. In the intact animal, velocity of circumferential fiber shortening (Vcf) was evaluated both before (n = 27, S = 12 and R = 15) and after myocardial infarction. Before infarction, increasing doses of isoproterenol provoked similar contractile and heart rate responses in each group of dogs. Either beta(1)-AR (bisoprolol) or beta(2)-AR (ICI-118551) antagonists reduced the isoproterenol response, with a larger reduction noted after the beta(1)-AR blockade. In contrast, after infarction, isoproterenol induced a significantly larger Vcf and heart rate response in the susceptible animals that was eliminated by beta(2)-AR blockade. The single-cell isotonic shortening response to isoproterenol (100 nM) was also larger in cells obtained from susceptible compared with resistant dogs and was reduced to a greater extent by beta(2)-AR blockade in the susceptible dog myocytes (S, -48%, n = 6; R, -15%, n = 9). When considered together, these data suggest that myocardial infarction provoked an enhanced beta(2)-AR response in susceptible, but not resistant, animals. |
3,692 | Influence of atrial fibrillation on outcome following mitral valve repair. | To investigate the outcome of patients in atrial fibrillation (AF) following mitral valve repair, clinical and echocardiographic follow-up was undertaken in 400 consecutive patients who underwent mitral valvuloplasty from 1987 to 1999.</AbstractText>The main indications for surgery were degenerative (81.4%), endocarditis (7.1%), rheumatic (6.6%), ischemic (4.6%), and traumatic (0.3%) mitral valve disease. After excluding 6 paced patients and 1 patient in nodal rhythm, we compared the outcomes of 152 patients in AF against 241 patients in sinus rhythm. For patients in AF versus those in sinus rhythm, more AF patients were older (mean age 67.2+/-8.8 versus 61.9+/-11.8 years, respectively; P<0.001), more were assigned to a poorer New York Heart Association (NYHA) class (77.6% versus 66.0% in NYHA III/IV, respectively; P=0.01), and more demonstrated impaired ventricular function (78.9% versus 46.2% with moderate or severe impairment, respectively; P<0.001). For patients in AF versus those in sinus rhythm, there was no difference in 30-day mortality (2.0% versus 2.1%, respectively; P=0.95), repair failure (5.4% versus 3.6%, respectively; P=0.41), stroke (5.4% versus 2.2%, respectively; P=0.11), or endocarditis (2.3% versus 0.9%, respectively; P=0.27) on follow-up at a median of 2.8 years (interquartile range 1.1 to 6.0). On echocardiography, the proportion of patients with mild regurgitation or worse was 13.3% (AF patients) versus 10.8% (patients in sinus rhythm) (P=0.70). Patients in AF versus those in sinus rhythm had lower survival at 3 years (83% versus 93%, respectively) and 5 years (73% versus 88%, respectively). Univariate analysis identified factors affecting survival as AF (P=0.002), age >70 years (P=0.041), and poor ventricular function (P<0.001). However, by use of a multivariate model, only poor ventricular function remained significant (P=0.01).</AbstractText>AF does not affect early outcome or durability of mitral repair. The onset of AF may be indicative of disease progression because of its association with poor left ventricular function.</AbstractText> |
3,693 | The effects of endothelin-1 on ischaemia-induced ventricular arrhythmias in rat isolated hearts. | We have shown previously that a small bolus dose of endothelin-1, given intravenously before coronary occlusion, exerts a marked antiarrhythmic effect in anaesthetised rats. The aim of the current study was to determine whether or not this is due to a direct effect of endothelin-1 on the heart by assessing the antiarrhythmic effect of endothelin-1 against occlusion-induced arrhythmias in rat isolated hearts. Rat isolated hearts were perfused in Langendorff mode (constant flow) and subjected to coronary artery occlusion for 30 min. Coronary perfusion pressure and a surface electrocardiogram (ECG) were monitored throughout the experiment. In the first series of studies, the effects of three 5-min infusions of endothelin-1 (0.1-10 nM), given prior to coronary occlusion, were assessed. A second series of hearts was given a single bolus dose of endothelin-1 (10 pmol) 5 min prior to ischaemia. A third series of experiments was performed using a modified (low K+) Krebs Henseleit solution to increase the incidence of ischaemia-induced ventricular fibrillation (VF). In these hearts, endothelin-1 (0.1 or 2 pmol) was administered as a bolus injection 5 min before ischaemia. Infusion of endothelin-1 prior to ischaemia did not modify the incidence or severity of arrhythmias at any of the concentrations used. Bolus administration of endothelin-1 (10 pmol) in hearts perfused with Kreb's Henseleit solution containing normal K+ (4.4 mM) was found to cause a small rise in coronary perfusion pressure, with no preceding depressor response. Under these conditions, endothelin-1 exerted only a very moderate reduction in arrhythmias, by reducing the arrhythmia count in the 21-30-min post-occlusion period. Furthermore, in hearts perfused with low K+ solution, bolus injection of endothelin-1, in a dose that either had no effect on coronary perfusion pressure (0.1 pmol) or produced a significant vasodilator effect with no significant pressor effect (2 pmol), had no effect on ventricular fibrillation. Thus, in concentrations that are sufficient to exert effects on the coronary vasculature, endothelin-1 fails to modify arrhythmias in an isolated heart preparation. These results suggest that the antiarrhythmic effects of endothelin-1 previously observed in vivo are not due to a direct effect on either the myocardium or the coronary blood vessels. |
3,694 | Angiotensin-(1-7): cardioprotective effect in myocardial ischemia/reperfusion. | In this study we evaluate the effects of angiotensin-(1-7) on reperfusion arrhythmias in isolated rat hearts. Rat hearts were perfused according to Langendorff technique and maintained in heated (37+/-1 degrees C) and continuously gassed (95% O(2)/5% CO(2)) Krebs-Ringer solution at constant pressure (65 mm Hg). The electrical activity was recorded with an ECG (bipolar). Local ischemia was induced by coronary ligation for 15 minutes. After ischemia, hearts were reperfused for 30 minutes. Cardiac arrhythmias were defined as the presence of ventricular tachycardia and/or ventricular fibrillation after the ligation of the coronary artery was released. Angiotensin II (0.20 nmol/L, n=10) produced a significant enhancement of reperfusion arrhythmias. On the other hand, Ang-(1-7) presented in the perfusion solution (0.22 nmol/L, n=11) reduced incidence and duration of arrhythmias. The antiarrhythmogenic effects of Ang-(1-7) was blocked by the selective Ang-(1-7) antagonist A-779 (2 nmol/L, n=9) and by indomethacin pretreatment (5 mg/kg IP, n=8) but not by the bradykinin B(2) antagonist HOE 140 (100 nmol/L, n=10) or by L-NAME pretreatment (30 mg/kg IP, n=8). These results suggest that the antiarrhythmogenic effect of low concentrations of Ang-(1-7) is mediated by a specific receptor and that release of endogenous prostaglandins.by Ang-(1-7) contributes to the alleviation of reversible and/or irreversible ischemia-reperfusion injury. |
3,695 | [Electrocardiographic changes during stress test in a patient with "Brugada syndrome"]. | We report a 28 year old man with the Brugada syndrome characterised by an electrocardiographic pattern of a right bundle branch block and an ST segment elevation in the right precordial leads as well as syncope. During an exercise test, we observed a normalization of the ST segment in V2+ while in the postexercise phase, the ST segment elevation in the right leads was established. This is the first case reported of the Brugada syndrome in Mexico, with spontaneous changes on the EKG masked during exercise and apparent during postexercise phase. |
3,696 | [Sudden death in intermittent Wolff Parkinson White syndrome]. | Sudden death is a rare condition in asymptomatic patients with asymptomatic intermittent Wolff Parkinson syndrome (WPW); for this reason it is believed that these patients should not undergo to radiofrequency ablation. We report an asymptomatic 44 year old man who developed ventricular fibrillation with a pre-excited RR interval less than 200 msec during atrial fibrillation, as a first manifestation of WPW syndrome. The Holter monitoring showed intermittent pre-excitation at low heart rate (70 bpm). During the electrophysiological study a successfully radiofrequency catheter ablation of a right posteroseptal accessory pathway was performed. We concluded that intermittent pre-excitation may not be used to identify patients who are at risk of sudden death. Radiofrequency catheter ablation should be recommended in those patients with a very high success rate, and a low incidence of serious complications. |
3,697 | [Atrial fibrillation]. | Atrial fibrillation (AF) is the most common sustained arrhythmia. AF has now been exhaustively studied: more is known about its mechanism and research is moving towards new forms of treatment. For chronic AF, basically the control of ventricular rate and the brain protection are the main issues. It is well known that with the identification of high risk group for embolism, oral anticoagulation should be administered. Ventricular rate control can be achieved by using betablockers or calcium channel blockers, unless these are contraindicated for the elderly. Oral anticoagulation prevents the stroke. The main mechanism of AF is the re-entry of multiple wavelets, but now it is more frequently found on patients with focal AF. Therapies are employed to bring the patient to a sinusal rhythm as soon as possible with antiarryhthmics or electric cardioversion externally or internally. The internal procedure includes 1 to 15 J and the success rate is of 91% vs 67% in relation to the external one. The introduction of the catheter ablation has opened new frontiers for the treatment of AF, first as the ablate-and-pace technique and now trying to mimic the maze procedure or with the ablation of the focal tachycardia. The stimulation for prevention of AF under research, as well as the implantable dysfibrillation for selected patients. On going studies will show the possible benefit of this type of benefits. |
3,698 | [Biatrial re-synchronization in the treatment of paroxysmal atrial fibrillation. 3- and 4-chamber pacemaker]. | The reason for multisite pacing is to correct atrial and ventricular electrical and mechanical asynchrony found in paroxysmal atrial fibrillation (PAF) and dilated cardiomyopathy. We report the first two cases in Mexico treated with biatrial pacing for PAF. The first was treated with a three chamber pacemaker and the other with a four chamber pacemaker. The first patient was a young man with uncontrolled ventricular rate in whom the atrioventricular conduction was modified with radiofrequency energy to control ventricular rate during atrial fibrillation. The second patient was a woman with corrected transposition of the great arteries, left ventricular ejection fraction (LVEF) of 30% and complete heart block. The pacing modalities were DDD for the first patient and DDDR for the second, both with sleep rate and auto mode switching. The atria were paced in right appendage and the left through the coronary sinus. PAF episodes were, found only in the first patient but were decreased in number and duration. The LVEF and functional class improved in the patient with biatrial and ventricular resynchronization. We conclude that biatrial pacing is effective in PAF. |
3,699 | Long-term efficacy and safety of propafenone and sotalol for the maintenance of sinus rhythm after conversion of recurrent symptomatic atrial fibrillation. | This study was performed to evaluate, using a randomized double-blind, placebo-controlled protocol, the long-term efficacy and safety of propafenone and sotalol in maintaining sinus rhythm after conversion of recurrent symptomatic atrial fibrillation (AF). The maintenance of sinus rhythm in patients with recurrent AF has several potential benefits, the most important being a reduced risk of thromboembolic events. Three hundred patients with recurrent AF (> or = 4 episodes in the last year) and AF at enrollment lasting < 48 hours were randomized to receive either propafenone (mean daily dose 13 +/- 1.5 mg/kg; 102 patients), sotalol (mean daily dose 3 +/- 0.4 mg/kg; 106 patients), or placebo (92 patients). After 1-year follow-up, Kaplan-Meier estimates of the proportion of patients remaining in sinus rhythm were comparable between propafenone (63%) and sotalol (73%) and superior to placebo (35%; p = 0.001 vs both drugs). Symptomatic recurrences occurred later with propafenone and sotalol than with placebo. Nine patients (9%) in the propafenone group, 11 (10%) in the sotalol group, and 3 (3%) in the placebo group discontinued therapy due to adverse effects. Malignant nonfatal arrhythmias due to proarrhythmic effects were documented with sotalol only, and occurred < 72 hours from the beginning of therapy in 4 patients (4%). During recurrences, the ventricular rate was significantly reduced in patients taking propafenone and sotalol (p = 0.001 for both drugs vs placebo). The likelihood of remaining in sinus rhythm during follow-up was higher in younger patients with smaller left atrial size and without concomitant heart disease. In patients with recurrent symptomatic AF, propafenone and sotalol are not significantly different from each other and are superior to placebo in maintaining sinus rhythm at 1 year. Recurrences occur later and tend to be less symptomatic with propafenone and sotalol compared with placebo. |
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