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2,200 | Neither vasopressin nor amiodarone improve CPR outcome in an animal model of hypothermic cardiac arrest. | Aim of this experimental animal study was to investigate the influence of vasopressin and amiodarone on cardiopulmonary resuscitation (CPR) outcome in a pig model of hypothermic cardiac arrest.</AbstractText>After surface cooling to a core temperature of 26 degrees C, ventricular fibrillation was induced in 14 12-16-week-old domestic pigs. After 15 min of untreated cardiac arrest, a manual closed chest CPR was started and pigs were randomly assigned to two treatment groups: Group 1 pigs (n = 7) received vasopressin 0.4 U kg-1 as initial drug therapy, followed by a combination vasopressin (0.4 U kg-1) and amiodarone (4 mg kg-1) as subsequent drug therapy. Subsequent drug therapy was administered in animals without permanent restoration of spontaneous circulation after a first series of electrical countershocks 10 min after drug administration. Group 2 pigs (n = 7) received saline placebo as initial drug therapy and saline placebo and amiodarone (4 mg kg-1) as subsequent drug therapy.</AbstractText>Vasopressin significantly increased coronary perfusion pressure and defibrillation success (successful defibrillation in five of seven Group 1 vs. none of seven Group 2 pigs, P = 0.02). Due to refibrillation within 30-150 s, the 60-min survival rate was not improved by vasopressin. Subsequent drug therapy with amiodarone had no further effect on defibrillation success or the refibrillation rate.</AbstractText>Data from this experimental animal model suggest that vasopressin and amiodarone may not be beneficial for treatment of ventricular fibrillation associated with severe hypothermia when concomitant measures at core rewarming are not applied.</AbstractText> |
2,201 | Arrhythmias in off-pump coronary artery bypass grafting and the antiarrhythmic effect of regional ischemic preconditioning. | The authors sought to establish whether regional ischemic preconditioning (IP) reduces ischemic reperfusion arrhythmias in patients who undergo off-pump coronary artery bypass grafting (OPCAB).</AbstractText>A controlled, randomized, prospective study.</AbstractText>A university hospital.</AbstractText>Thirty-two patients with left anterior descending coronary artery (LAD) or 2-vessel heart disease (including LAD) who were to undergo OPCAB were randomized into an IP and a control group.</AbstractText>IP was induced by occluding the LAD twice for a 2-minute period followed by 3-minute LAD reperfusion before bypass grafting of the first coronary vessel.</AbstractText>Twenty-four-hour electrocardiography was recorded from the preoperative day to the second postoperative day. The heart rate (HR) was significantly elevated after surgery. Supraventricular extrasystole (SVES) events were similar before and after surgery. The incidence of patients with ventricular extrasystole (VES), supraventricular tachycardia (SVT), atrial fibrillation (AF), and ventricular tachycardia (VT) was significantly increased after the operation. Ventricular arrhythmias occurred mostly during anastomosis and the early reperfusion period and recovered 2 hours after reperfusion. Supraventricular tachyarrhythmias were mostly encountered 24 hours after reperfusion. IP significantly suppressed HR elevation, SVT, and VT after surgery. SVES, VES, and AF episodes were similar between the groups.</AbstractText>Arrhythmia was a common phenomenon during and after an OPCAB procedure. The present IP protocol significantly suppressed HR elevation, the episodes of SVT, and the incidence of VT after surgery.</AbstractText> |
2,202 | Heart block, ventricular tachycardia, and sudden death in ACE2 transgenic mice with downregulated connexins. | Angiotensin converting enzyme related carboxypeptidase (ACE2) is a recently discovered homolog of angiotensin converting enzyme with tissue-restricted expression, including heart, and the capacity to cleave angiotensin peptides. We tested the hypothesis that cardiac ACE2 activity contributes to features of ventricular remodeling associated with the renin-angiotensin system by generating transgenic mice with increased cardiac ACE2 expression. These animals had a high incidence of sudden death that correlated with transgene expression levels. Detailed electrophysiology revealed severe, progressive conduction and rhythm disturbances with sustained ventricular tachycardia and terminal ventricular fibrillation. The gap junction proteins connexin40 and connexin43 were downregulated in the transgenic hearts, indicating that ACE2-mediated gap junction remodeling may account for the observed electrophysiologic disturbances. Spontaneous downregulation of the ACE2 transgene in surviving older animals correlated with restoration of nearly normal conduction, rhythm, and connexin expression. |
2,203 | [Determinants of paroxysmal atrial fibrillation in patients with arterial hypertension]. | Atrial fibrillation represents an important arrhythmia, in particular in patients with arterial hypertension. Hitherto, the connection between paroxysmal atrial fibrillation, left atrial size and left ventricular muscle mass has not been investigated sufficiently. In the present study, determinants of paroxysmal atrial fibrillation in patients with arterial hypertension were evaluated.</AbstractText>104 consecutive patients were enrolled into this study. All of them suffered from arterial hypertension for more than one year. Persistent or permanent atrial fibrillation was not documented. In all of these patients, clinical, echocardiographic and rhythmologic variables were evaluated.</AbstractText>In 10.3% of the patients, paroxysmal atrial fibrillation was found. These patients showed a significantly larger left atrium (43.3 +/- 6.7 vs 37.5 +/- 4.9 mm, p < 0.001), a significantly higher muscle mass of the left ventricle (152.38 +/- 43.57 vs 134.41 +/- 27.19 g/m2, p < 0.01) and significantly more frequent a mild mitral regurgitation (38.1 vs 28.6%, p < 0.01). The multivariate regression analysis revealed as independent factors for paroxysmal atrial fibrillation the size of the left atrium and the presence of mild mitral regurgitation. Independent factors for an enlarged left atrium were mitral insufficiency and left ventricular muscle mass.</AbstractText>This study shows that paroxysmal atrial fibrillation in aterial hypertension is based on the left atrial size, and left atrial size on left ventricular muscle mass. Therefore, these results should lead to a causal therapy for treatment of paroxysmal atrial fibrillation in these patients.</AbstractText> |
2,204 | [Detection of atrial late potentials with P wave signal averaged electrocardiogram among patients with paroxysmal atrial fibrillation]. | The analysis of the QRS-complex with signal averaged ECG (SAECG) has been evaluated for patients affected by ventricular tachycardia for a long time. A longer filtered QRS-complex was a marker of a slower ventricular conduction velocity and reentry tachycardia. This method was modified for an analysis of the P wave (P-SAECG). Different filter methods were evaluated for the analysis of atrial late potentials.</AbstractText>We measured the bidirectional P wave signal averaged ECG of 45 consecutive patients with (group A) and without (group B) paroxysmal atrial fibrillation (PAF) and 15 young volunteers without a cardiac disease (group C).</AbstractText>As a result patients with PAF had a significantly lower root mean square voltage of the last 20 ms (RMS 20) (2.59 +/- 0.89) vs 4.08 +/- 1.45 microV, p < 0.0003) and a significantly longer filtered P wave duration (FPD) than patients of the control collective (139.2 +/- 17.5 vs 115.1 +/- 17.7 ms, p < 0.0001) and the young volunteers (3.44 +/- 0.95 microV, p < 0.0001/101.9 +/- 14.2 ms, p < 0.009). Furthermore we found an age-dependent relationship of FPD between group B and C (115.1 +/- 17.7 vs 101.9 +/- 14.2 ms, p < 0.05) but not an age-dependent relationship of the RMS 20 (4.08 +/- 1.45 vs 3.44 +/- 0.95 microV, p = n.s.). A specificity of 80% and a sensitivity of 78% was achieved for identifying patients with atrial fibrillation by using a definition of atrial late potentials as FPD > 120 ms and a RMS 20 < 3.5 microV.</AbstractText>The analysis of the P-SAECG can be used as a non-invasive method for identifying atrial late potentials. Atrial late potentials might be a reason for PAF. The predictive power of atrial late potentials has to be examined by prospective investigations of a larger patient population.</AbstractText> |
2,205 | [Changes in cardiac resistance to arrhythmogenic effects during ATP-dependent K+ channel activation]. | It has been found that pretreatment with ATP-dependent potassium channel (KATP-channel) opener, BMS 180448 (3 mg/kg, intravenously), increases cardiac resistance against arrhythmogenic action of coronary artery occlusion and reperfusion in anaesthetized rats. However, BMS 180448 induced a decrease in ventricular fibrillation threshold in rats postinfarction cardiac fibrosis. This effect was completely abolished by administration of the KATP-channel inhibitor, glibenclamide. By contrast, coadministration of BMS 180448 and selective sarcolemmal KATP-channel inhibitor, HMR 1098, promoted an increase in ventricular fibrillation threshold in rats with postinfarction cardiac fibrosis before normal value. The selective mitochondrial KATP-channel opener, diazoxide, also exacerbated a decrease in ventricular fibrillation threshold induced by postinfarction cardiac sclerosis. But after depletion of endogenous catecholamine storage by pretreatment with guanthidine, diazoxide, on the contrary, elevated the ventricular fibrillation threshold. It has been suggested that stimulation of mitochondrial ATP-sensitive potassium channels promotes an elevation in electrical stability of the heart, whereas opening of sarcolemmal KATP-channel increases a possibility of ventricular arrhythmias. |
2,206 | ECG interpretation: what is different in children? | While the electrical waveforms and basic approach to electrocardiogram (ECG) interpretation are similar for pediatric and adult patients, some important differences must be recognized to provide appropriate care for infants and children. Maturational changes that occur over the early childhood years result in differences in normal heart rates, interval durations, and ventricular dominance. Any arrhythmia seen in adults can occur in the pediatric patient; however, the most common variations from normal rhythms are sinus arrhythmia, bradycardia, and supraventricular tachycardia. Nurses caring for infants and children must recognize the important similarities and differences in rhythm strip interpretation between the adult and the pediatric patient. |
2,207 | [Factors for successful conversion of atrial fibrillation using intravenous injection of pilsicainide hydrochloride]. | The factors affecting successful conversion of atrial fibrillation using intravenous injection of pilsicainide hydrochloride are unclear. The efficacy of intravenous injection of pilsicainide hydrochloride and the factors affecting successful conversion of symptomatic atrial fibrillation were investigated.</AbstractText>Twenty-six patients[21 men, 5 women, 64 +/- 12 years (mean +/- SD)] with electrocardiographically confirmed, symptomatic atrial fibrillation were treated with intravenous injection 1.0 mg/kg of pilsicainide hydrochloride between October 31, 2000 and February 17, 2003. Successful conversion was defined as termination of atrial fibrillation within 30 min of intravenous injection. Before the injection of pilsicainide hydrochloride, blood pressure, conventional electrocardiography, chest radiography, echocardiography and blood examinations were performed. During and after injection of pilsicainide hydrochloride, blood pressure and conventional electrocardiography were monitored. After injection of pilsicainide hydrochloride, blood examinations were performed.</AbstractText>Pharmacological conversion to sinus rhythm was achieved in 7 of 26 patients(27%). The successful conversion group and unsuccessful conversion group showed significant differences in duration of atrial fibrillation(61 +/- 122 vs 12,257 +/- 25,959 hr, p < 0.01), heart rates before injection of pilsicainide (110 +/- 26 vs 87 +/- 26 beats/min, p < 0.05), cardiothoracic ratio(47.8 +/- 2.6% vs 53.5 +/- 5.1%, p < 0.01) and left atrial dimension(38 +/- 7 vs 45 +/- 6 mm, p < 0.05).</AbstractText>Pilsicainide hydrochloride is effective in patients with atrial fibrillation of short duration with small left atrium and rapid ventricular response.</AbstractText> |
2,208 | [Impaired left ventricular systolic function in mitral stenosis]. | Left ventricular dysfunction is known in patients with mitral stenosis, but the incidence and cause remain unclear. The incidence and the factors related to left ventricular dysfunction were investigated in strictly selected patients with isolated mitral stenosis.</AbstractText>This study investigated 33 patients (5 males, 28 females) with isolated mitral stenosis aged 56 +/- 9 years. Left atrial dimension, left ventricular diastolic and systolic dimensions, mitral valve area, and mean transmitral pressure gradient were measured by echocardiography. Left ventricular ejection fraction was measured by Simpson's method. Patients were divided into two groups according to the ejection fraction (< 50%, > or = 50%).</AbstractText>Seven patients (21%) had decreased left ventricular contraction and 26(79%) had normal contraction. The incidence of patients with atrial fibrillation in the low ejection fraction group was significantly higher than in the normal ejection fraction group(86% vs 31%, p < 0.01). There were no significant differences in the severity of mitral stenosis or other echocardiographic indices between the two groups.</AbstractText>Low ejection fraction was present in 21% of patients with mitral stenosis. Since atrial fibrillation was more common in patients with low ejection fraction than those with normal ejection fraction, the rhythm disturbance may be related to the decreased left ventricular contraction.</AbstractText> |
2,209 | Differential diagnosis and clinical course of amiodarone-induced thyroid dysfunction. | Amiodarone is an iodine-rich drug widely used for the management of various arrhythmias, but its clinical utility is usually limited by the high frequency of numerous side effects, most frequently disturbance of thyroid function.</AbstractText><AbstractText Label="MATERIAL/METHODS" NlmCategory="METHODS">The present study presents the laboratory tests, color flow Doppler sonography (CFDS) findings, treatment and prognosis of 22 patients with amiodarone-induced thyroid dysfunction.</AbstractText>Eleven patients developed amiodarone- induced thyrotoxicosis (AIT), ten developed amiodarone-induced hypothyroidism (AIH) and one patient first developed AIT, followed by AIH. Age, amiodarone doses, duration of amiodarone treatment and discontinuation of amiodarone were similar in the patients with AIT and AIH. AIT was found more commonly in male patients, AIH in female patients. Color flow Doppler sonographic examination was performed in all patients with AIT to differentiate type 1 and 2 AIT. In ten patients, CFDS demonstrated increased glandular vascularity, diagnostic for type 1 AIT.</AbstractText>This paper presents patients with AIT treated successfully with propylthiouracil or prednisolone after developing thyroid dysfunction as a consequence of amiodarone use. The role of thyroid Doppler in managing these patients is emphasized.</AbstractText> |
2,210 | Heme oxygenase-1-related carbon monoxide production and ventricular fibrillation in isolated ischemic/reperfused mouse myocardium. | Heme oxygenase-1 (HO-1)-dependent carbon monoxide (CO) production related to reperfusion-induced ventricular fibrillation (VF) was studied in HO-1 wild-type (+/+), heterozygous (+/-), and homozygous (-/-) isolated ischemic/reperfused mouse heart. In HO-1 homozygous myocardium, under aerobic conditions, HO-1 enzyme activity, HO-1 mRNA, and protein expression were not detected in comparison with aerobically perfused wild-type and heterozygous myocardium. In wild-type, HO-1 hetero- and homozygous hearts subjected to 20 min ischemia followed by 2 h of reperfusion, the expression of HO-1 mRNA, protein, and HO-1 enzyme activity was detected in various degrees. A reduction in the expression of HO-1 mRNA, protein, and enzyme activity in fibrillated wild-type and heterozygous myocardium was observed. In reperfused/nonfibrillated wild-type and heterozygous hearts, a reduction in HO-1 mRNA, protein expression, and HO-1 enzyme activity was not observed, indicating that changes in HO-1 mRNA, protein, and enzyme activity could be related to the development of VF. These changes were reflected in the HO-1-related endogenous CO production measured by gas chromatography. In HO-1 knockout ischemic/reperfused myocardium, all hearts showed VF, and no detection in HO-1 mRNA, protein, and enzyme activity was observed. Thus, interventions that are able to increase endogenous CO may prevent the development of VF. |
2,211 | Determinants of LV diastolic function during atrial fibrillation: beat-to-beat analysis in acute dog experiments. | Left ventricular (LV) diastolic function during atrial fibrillation (AF) remains poorly understood due to the complex interaction of factors and beat-to-beat variability. The purpose of the present study was to elucidate the physiological determinants of beat-to-beat changes in LV diastolic function during AF. The RR intervals preceding a given cardiac beat were measured from the right ventricular electrogram in 12 healthy open-chest mongrel dogs during AF. Doppler echocardiography and LV pressure and volume beat-to-beat analyses were performed. The LV filling time (FT) and early diastolic mitral inflow velocity-time integral (E(vti)) were measured using the pulsed Doppler method. The LV end-diastolic volume (EDV), peak systolic LV pressure (LVP), minimum value of the first derivative of LV pressure curve (dP/dt(min)), and the time constant of LV pressure decay (tau) were evaluated with the use of a conductance catheter for 100 consecutive cardiac cycles. Beat-to-beat analysis revealed a cascade of important causal relations. LV-FT showed a significant positive linear relationship with E(vti) (r = 0.87). Importantly, there was a significant positive linear relationship between the RR interval and LV-EDV in the same cardiac beat (r = 0.53). Consequently, there was a positive linear relationship between LV-EDV and subsequent peak systolic LVP (r = 0.82). Furthermore, there were significant positive linear and negative curvilinear relationships between peak systolic LVP and dP/dt(min) (r = 0.95) and tau (r = -0.85), respectively, in the same cardiac beat. In addition, there was a significant negative curvilinear relationship between dP/dt(min) and tau (r = -0.86). We have concluded that the determinants of LV diastolic function in individual beats during AF depend strongly on the peak systolic LVP. This suggests that the major benefit of slower ventricular rate appears related to lengthening of LV filling interval, promoting subsequent higher peak systolic LVP and greater LV relaxation. |
2,212 | Cardiac changes in subclinical and overt hyperthyroid women: retrospective study. | This retrospective and descriptive 4-year study was undertaken to describe cardiac changes in subclinical and overt hyperthyroidism.</AbstractText>We revised the charts of 386 consecutive cardiopathic women whose blood samples were referred to the Radioimmunoassay Laboratory to evaluate thyroid function from 1 January 1997 through 31 December 2000.</AbstractText>After excluding women because euthyroid or hypothyroid, or taking amiodarone and women with hypertension, rheumatic disease, myocardial infarction, a total of 31 hyperthyroid women were thus selected for the study: 19 with subclinical hyperthyroidism and 12 with overt hyperthyroidism. The prevalence of atrial fibrillation did not differ between subclinical (48%) and overt (67%) hyperthyroid women, as well as left atrial dimension; the latter was larger in hyperthyroid (27.8+/-7.8 cm(2)/m(2)) than in control women (18.9+/-2.8 cm(2)/m(2)) (P<0.001). In the subclinical and overt hyperthyroidism, the heart rate (HR) was increased and left ventricular end diastolic (LVED) volume was reduced; in addition, only in overt hyperthyroidism, left ventricular (LV) mass was increased. A significant correlation between LV mass and free triiodothyronine was found.</AbstractText>HR increase and LVED decrease, both in subclinical and overt hyperthyroidism, indicate a global impairment of diastolic heart performance, complicated in overt hyperthyroidism by LV concentric hypertrophy. So, in our opinion, subclinical hyperthyroidism, far from being considered a simple laboratory finding, in clinical practice should be taken into serious consideration.</AbstractText> |
2,213 | Spontaneous echo contrast in the descending aorta in patients without aortic dissection: associated clinical and echocardiographic characteristics. | The objective of the study was to evaluate the frequency, clinical and echocardiographic correlates of spontaneous echo contrast in the descending aorta in the absence of dissection. Prevalence of spontaneous echo contrast in the descending aorta in the absence of dissection, and its clinical and echocardiographic correlates were investigated in 1199 consecutive patients who underwent transesophageal echocardiography. Spontaneous echo contrast in the descending aorta was detected in 54 (4.5%) patients. Patients with spontaneous echo contrast in the descending aorta had an older age (60.6+/-8 vs. 40.6+/-14.2 years, P=0.0001), an increased prevalence of male gender (66.7 vs. 43.9%, P=0.001), an increased diameter of ascending aorta (4.2+/-1.0 vs. 3.3+/-1.1 cm, P=0.0001), an increased diameter of descending aorta (3.1+/-0.9 vs. 2.1+/-0.4 cm, P=0.0001), a higher prevalence of aortic wall calcification (9.3 vs. 0.5%, P=0.00001), complex plaque in the descending aorta (13 vs. 0.7%, P=0.0001), left ventricular dysfunction (7.4 vs. 2.1%, P<0.05), a lower incidence of severe aortic regurgitation (0 vs. 3.5%, P<0.05), a lower peak flow velocity in the descending aorta (28+/-9 vs. 51+/-21 cm/s, P<0.00001), and a lower maximal shear rate in the descending aorta (51+/-29 vs. 105+/-47 s(-1), P<0.00001) compared with patients without spontaneous echo contrast in the descending aorta. However, prevalence of atrial fibrillation, mitral valve disease, intracardiac spontaneous echo contrast and/or thrombus and embolic event were not different between patients with and without spontaneous echo contrast in the descending aorta (P>0.05). Shear rate, diameter of the descending aorta, aortic wall calcification, complex plaque in the descending aorta, absence of severe aortic regurgitation and male gender were independent variables of spontaneous echo contrast in the descending aorta. Spontaneous echo contrast in the descending aorta is a local and flow-dependent phenomenon related to aortic dilation, atherosclerosis, and decreased shear rates in the descending aorta. However, in this study, spontaneous echo contrast in the descending aorta was not found to be associated with embolic events. |
2,214 | Evaluation of P wave duration and P wave dispersion in adult patients with secundum atrial septal defect during normal sinus rhythm. | Paroxysmal atrial arrhythmias especially atrial fibrillation (AF) are frequently encountered in adult patients with atrial septal defect (ASD). Previously it was shown that maximum P wave duration and P wave dispersion in 12-lead surface electrocardiograms are significantly increased in individuals with a history of paroxysmal AF. The aim of this study was to determine whether P maximum and P dispersion in adult patients with ASD and without AF are increased as compared to healthy controls. In addition, the relationship of pulmonary to systemic flow ratio (Qp/Qs) and these P wave indices were investigated.</AbstractText>Sixty-two consecutive patients [39 women, 23 men; mean age 33+/-13 years (range 16 to 61 years)] with ostium secundum type ASD and 47 healthy subjects [25 women, 22 men; mean age 36.6+/-9.5 years (range 18 to 50 years)] were investigated. P maximum, P minimum and P dispersion (maximum minus minimum P wave duration) were measured from the 12-lead surface ECG. There were no significant differences with respect to age (P=0.08), gender (P=0.3), heart rate (P=0.3), left atrial diameter (P=0.5) and left ventricular ejection fraction (P=0.3) between patients and controls. Pulmonary artery peak systolic pressure was significantly higher in patients with ASD as compared to controls (P<0.0001). P maximum was significantly longer in patients with ASD as compared to controls (P<0.0001). In addition, P dispersion of the patients was significantly higher than controls (P=0.001). P minimum was not different between groups (P=0.12). Mean Qp/Qs of the patients with ASD was 2.5+/-0.7 (minimum 1.5; maximum 4.1) and found to be significantly correlated with P maximum (r=0.34; P=0.006) and P dispersion (r=0.61; P<0.0001).</AbstractText>Prolongation of P maximum and increased P dispersion could represent mechanical and electrical changes of atrial myocardium in patients with ASD. These changes of atrial myocardium may be more prominent with higher left to right shunt volumes.</AbstractText> |
2,215 | Left atrioventricular plane displacement predicts cardiac mortality in patients with chronic atrial fibrillation. | The aim of the present study was to investigate if left atrioventricular plane displacement (AVPD) has a prognostic value in patients with atrial fibrillation.</AbstractText>Left AVPD was assessed by two-dimensionally guided M-mode echocardiography in the four- and two-chamber views in 160 consecutive patients with chronic atrial fibrillation, who were followed up with regard to mortality for an average of 45 months. All-cause mortality during follow-up was 49% (n=78). AVPD was lower in patients who died compared to those who survived: 6.6+/-1.7 versus 7.5+/-1.7 mm, P=0.0005. In 49 patients (31%), death was due to chronic heart failure or acute myocardial infarction. Among those who died of cardiac events, AVPD was 6.3+/-1.6 mm, versus 7.1+/-1.8 mm among those who died of other causes, P=0.0001. In multiple logistic regression analysis, AVPD (P=0.005), age (P=0.0005), and a history of chronic heart failure (P=0.004) correlated independently with mortality.</AbstractText>Left AVPD was clearly decreased in patients with atrial fibrillation. The decrease was most pronounced in patients who died of cardiac events, whereas it did not differ significantly between those who died of non-cardiac causes and those who survived. The discriminative value of left AVPD was limited.</AbstractText> |
2,216 | Equine athletes, the equine athlete's heart and racing success. | Our recent data have confirmed that maximum oxygen delivery in racing Thoroughbreds is positively correlated to left ventricular mass measured by echocardiography. A similar, but weaker relationship also exists between left ventricular mass and Timeform performance rating in commercial racehorses. The relationship of the Thoroughbred heart to racing success and the special problems that selective breeding for aerobic capacity have had in this species are reviewed in this article. |
2,217 | Biphasic or monophasic defibrillation for adult ventricular fibrillation. | A short cut review was carried out to establish whether biphasic defibrillatory shocks were superior to monophasic shocks in patients in ventricular fibrillation. Altogether 337 papers were found using the reported search, of which seven presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. A clinical bottom line is stated. |
2,218 | Percutaneous pericardial instrumentation for endo-epicardial mapping of previously failed ablations. | The epicardial location of an arrhythmia could be responsible for unsuccessful endocardial catheter ablation.</AbstractText>In 48 patients referred after prior unsuccessful endocardial ablation, we considered percutaneous, subxiphoid instrumentation of the pericardial space for mapping and ablation. Thirty patients had ventricular tachycardia (VT), 6 patients had a right- and 4 had a left-sided accessory pathway (AP), 4 patients had inappropriate sinus tachycardia, and 4 patients had atrial arrhythmias. Of the 30 VTs, 24 (6 with ischemic cardiomyopathy, 3 with idiopathic cardiomyopathy, and 15 with normal hearts) appeared to originate from the epicardium. Seventeen (71%) of these 24 VTs were successfully ablated with epicardial lesions. The other 7 VTs had early epicardial sites that were inaccessible, predominantly because of interference from the left atrial appendage. Six of these were successfully ablated from the left coronary cusp. In 5 of the 10 patients with an AP, the earliest activation was recorded epicardially. Three of these were right atrial appendage-to-right ventricle APs, and epicardial ablation was successful. No significant complications were observed.</AbstractText>Failure of endocardial ablation could reflect the presence of an epicardial arrhythmia substrate. Epicardial instrumentation and ablation appeared feasible and safe and provided an alternative strategy for the treatment of patients with a variety of arrhythmias. This was particularly true for VT, including patients without structural heart disease.</AbstractText> |
2,219 | Electrical remodeling of the atria in congestive heart failure: electrophysiological and electroanatomic mapping in humans. | Atrial fibrillation (AF) frequently complicates congestive heart failure (CHF). However, the electrophysiological substrate for AF in humans with CHF remains unknown. We evaluated the electrophysiological and electroanatomic characteristics of the atria in patients with CHF.</AbstractText>Twenty-one patients (aged 53.7+/-13.6 years) with symptomatic CHF (left ventricular ejection fraction 25.5+/-6.0%) and 21 age-matched controls were studied. The following were evaluated: effective refractory periods (ERPs) from the high and low lateral right atrium (LRA), high septal right atrium, and distal coronary sinus (CS); conduction time along the CS and LRA; corrected sinus node recovery times; P-wave duration; and conduction at the crista terminalis. In a subset, electroanatomic mapping was performed to determine atrial activation, regional conduction velocity, double potentials, fractionated electrograms, regional voltage, and areas of electrical silence. Patients with CHF demonstrated an increase in atrial ERP with no change in the heterogeneity of refractoriness, an increase of atrial conduction time along the LRA and the CS, prolongation of the P-wave duration and corrected sinus node recovery times, and greater number and duration of double potentials along the crista terminalis. Electroanatomic mapping demonstrated regional conduction slowing with a greater number of electrograms with fractionation or double potentials, associated with areas of low voltage and electrical silence (scar). Patients with CHF demonstrated an increased propensity for AF with single extrastimuli, and induced AF was more often sustained.</AbstractText>Atrial remodeling due to CHF is characterized by structural changes, abnormalities of conduction, sinus node dysfunction, and increased refractoriness. These abnormalities may be responsible in part for the increased propensity for AF in CHF.</AbstractText> |
2,220 | Sleep quality among patients treated with implantable atrial defibrillation therapy: effect of nocturnal shock delivery and psychological distress. | The Medtronic ICD-AT has atrial/ventricular therapies, which can be programmed to deliver atrial defibrillation during sleep, intended to potentially decrease shock anxiety/pain and lifestyle disruption. However, these shocks may diminish sleep quality. This study examined atrial shock characteristics (i.e., mode, frequency), AF symptoms, and psychological factors as determinants of sleep quality.</AbstractText>The 96 ICD-AT patients were mostly men (72%; M age 65 +/- 12 years) and implanted for 1.6 years (SD = 0.8 years). Patients were divided into shock groups based on the proportion of mode (> or =90%) of total atrial shocks received. Patients were grouped into either automatic-nocturnal shock group (8 P.M.-8 A.M.; n = 35) or manual-awake shock group (n = 42). Psychological measures included Pittsburgh Sleep Quality Index (PSQI), Center for Epidemiology Studies-Depression Scale, State-Trait Anxiety Inventory, and Illness Intrusiveness Rating Scale. Atrial fibrillation disease burden was assessed via atrial symptom score and atrial shock use. PSQI global scores were similar between manual (7.67 +/- 2.53) and automatic shock (8.20 +/- 2.93) groups. A multiple hierarchical regression analysis indicated that no atrial shock variables were predictive of sleep quality; yet, both AF symptom (B = 0.226, P = 0.040) and depression (B = 0.392, P = 0.034) scores predicted diminished sleep quality, accounting for 42% of the variance in global sleep quality (P < 0.001).</AbstractText>These results suggest that atrial defibrillation therapy does not have a deleterious impact on sleep. However, the significance of AF symptoms and depression indicate that comprehensive care of both physical and psychological symptomatology may improve sleep quality in ICD-AT patients.</AbstractText> |
2,221 | Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. | The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood.</AbstractText>The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia.</AbstractText>Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided.</AbstractText> |
2,222 | Ventricular flutter induced during electrophysiologic studies in patients with old myocardial infarction: clinical and electrophysiologic predictors, and prognostic significance. | Induction of ventricular flutter during electrophysiologic (EP) studies (similar to that of ventricular fibrillation [VF]) often is viewed as a nonspecific response with limited prognostic significance. However, data supporting this dogma originate from patients without previously documented ventricular tachyarrhythmias. We examined the significance of ventricular flutter in patients with and without spontaneous ventricular arrhythmias.</AbstractText>We conducted a cohort study of all patients with myocardial infarction (MI) undergoing EP studies at our institution. Of 344 consecutive patients, 181 had previously documented spontaneous sustained ventricular arrhythmias, 61 had suspected ventricular arrhythmias, and 102 had neither. Ventricular flutter was induced in 65 (19%) of the patients. Left ventricular ejection fraction was highest among patients with inducible VF (35 +/- 13), lowest for patients with inducible sustained monomorphic ventricular tachycardia (SMVT; 27 +/- 9), and intermediate for patients with inducible ventricular flutter (30 +/- 10). Similarly, the coupling intervals needed to induce the arrhythmia were shortest for VF (200 +/- 28 msec), intermediate for ventricular flutter (209 +/- 27 msec), and longest for SMVT (230 +/- 35 msec). During 5 +/- 8 years of follow-up, the risk for ventricular tachycardia/VF was high for patients with SMVT and ventricular flutter and low for patients with inducible VF and noninducible patients (46%, 34%, 17%, and 14%, P < 0.005).</AbstractText>Patients with inducible ventricular flutter appear to be "intermediate" between patients with inducible VF and patients with SMVT in terms of clinical and electrophysiologic correlates. However, the prognostic value of inducible ventricular flutter is comparable to that of SMVT.</AbstractText> |
2,223 | Cost-effectiveness of the implantable cardioverter defibrillator: a review of current evidence. | Implantable cardioverter defibrillator (ICD) therapy is indicated for patients at risk for sudden cardiac death (SCD) due to ventricular tachycardia (VT) or ventricular fibrillation (VF). The high relative cost of therapy with the ICD versus antiarrhythmic drugs has raised questions regarding its cost-effectiveness. To address these questions, we review the literature on ICD cost-effectiveness.</AbstractText>MEDLINE and other databases were searched for articles published since 1980 reporting original data on the cost-effectiveness of ICD versus drug therapy for patients at risk for SCD. Data on costs and life-years were abstracted and studies grouped into decision analysis models and trial-based analyses. Cost-effectiveness ratios were inflated to 2002 US dollars. Thirteen economic studies were included in this review: 6 decision-analytic models, 4 economic analysis alongside randomized controlled trials, and 1 observational study. Two additional studies evaluated the cost-effectiveness of ICDs stratified by mortality risk. Studies varied in time horizon, and in all but one study ICD therapy was more costly than drug therapy. Early models assumed larger survival benefits than were observed in subsequent trials; therefore, ICDs appeared to be more cost-effective (i.e., US dollars 28000-US dollars 60000 per life-year gained). Three large clinical trial-based studies estimated that the cost per life-year gained was between US dollars 30181 and US dollars 185000. Stratified analyses show that patients at higher risk for mortality due to structural heart disease (e.g., left ventricular ejection fraction <35%) benefit more from ICD therapy, resulting in lower cost-effectiveness ratios.</AbstractText>ICD therapy continues to evolve with changing methods of implantation and improving technology. Current evidence suggests that ICDs may be a cost-effective option in patients at high risk for VT/VF. The cost-effectiveness of ICD therapy for primary and secondary prevention of SCD depends upon patient characteristics that influence their prior risk of mortality. Further research on patient selection criteria and the measurement of health-related quality of life is required.</AbstractText> |
2,224 | Use of nonantiarrhythmic drugs for prevention of sudden cardiac death. | It is of interest that the drugs having the most significant impact on total and sudden death mortality are those without direct electrophysiologic actions on myocardial excitable tissue. This observation may provide insight into mechanisms responsible for ventricular tachyarrhythmias causing cardiac arrest. One way to think about ventricular fibrillation is that it is the final common pathway of an electrically unstable heart. After all, the heart can "die" in only three major ways: electromechanical dissociation, asystole and heart block, and ventricular fibrillation, with the latter most common. It is the "upstream" events provoking the electrical instability that these drugs probably act upon (i.e., ischemia, fibrosis). Although we unquestionably need to pursue investigations into the electrophysiology of these ventricular tachyarrhythmias, more studies need to investigate the drugs affecting upstream events, because these agents appear to yield the greatest dividends, at least for the present. This article reviews these drugs and how they may be effective. |
2,225 | Role of amiodarone in the era of the implantable cardioverter defibrillator. | Amiodarone is one of the most frequently used antiarrhythmic drugs in clinical practice. In patients with atrial fibrillation, in whom rhythm control is judged desirable, amiodarone is the most effective therapy. Amiodarone effectively prevents atrial fibrillation and may improve quality of life, but there is no evidence that it decreases mortality or severe morbidity in atrial fibrillation. In patients at risk for life-threatening ventricular arrhythmias, amiodarone may decrease mortality to a small degree, but the evidence for this benefit is incomplete. Patients with implantable cardioverter defibrillators frequently require antiarrhythmic drug therapy, especially to treat electrical storm. Amiodarone is useful in these patients; however, it may increase defibrillation thresholds in some patients. In patients with out-of-hospital DC shock-resistant VF, amiodarone is the most effective antiarrhythmic drug available to assist in resuscitation. Amiodarone is a complicated drug, and its optimal use requires careful patient surveillance with respect to potential adverse effects. |
2,226 | Curative ablation for atrial fibrillation: what clinical trials do we need to establish efficacy. | In contrast to other supraventricular tachycardias, curative treatment of atrial fibrillation, although increasingly available and rapidly evolving, is neither as effective nor the first choice. Until recently, the unavailability of nonsurgical curative treatment may have fueled a debate on the relative importance of restoring sinus rhythm versus controlling the ventricular rate during atrial fibrillation. Recent randomized trials (PIAF, AFFIRM, and RACE) using very limited atrial fibrillation burden assessment show that pharmacologic ventricular rate control is much safer and possibly more effective than pharmacologic restoration of sinus rhythm. A clinical trial comparing a truly curative treatment of atrial fibrillation-such as catheter ablation targeting pulmonary vein isolation-with pharmacologic treatment is required. It should focus on reliable efficacy parameters, use vigilant assessment of safety, and, most importantly, be structured to provide all-important prognostic information on long-term outcome. Atrial fibrillation burden is a theoretically robust efficacy parameter, but accurate quantification over a sufficiently long period of monitoring will require technologically innovative noninvasive rhythm monitoring devices. |
2,227 | Increased QT dispersion in epileptic children. | Epilepsy is a common paroxysmal disorder in childhood. Tachyarrhythmia, bradyarrhythmia, asystole, atrioventricular block, ventricular fibrillation or sudden death may occur during seizures. Mutations of ion-channel coding genes are found in patients with idiopathic or cryptogenic epilepsy. The ion channels also play a role in arrhythmogenesis. QT dispersion is a non-invasive method for assessment of regional repolarization differences within the myocardial tissue. This study investigated QT and QTc dispersion (QTcd) and the risk of dysrhythmia in epileptic children.</AbstractText>The first group included 28 patients with newly diagnosed epilepsy and not taking antiepileptic treatment (range 10 mo to 15 y, mean +/- SD 6.86 +/- 3.92 y), the second group included 34 patients taking antiepileptic treatment (range 1-14 y, mean +/- SD 7.51 +/- 3.68 y) and the control group included 52 healthy children (range 4 mo to 15 y, mean +/- SD 6.94 +/- 3.92 y). Twelve-lead ECGs were obtained and heart rate, RR interval, P wave amplitude and duration, PR interval, QRS duration, QRS axis and QT intervals were measured, and QTc, QTd, QTcd were calculated in all subjects. The measurements were repeated in the first group under antiepileptic treatment.</AbstractText>While no significant difference in terms of heart rate, RR interval, P wave amplitude and duration, PR interval, QRS duration, QRS axis, QT intervals or QTc intervals was found, QTd and QTcd values were significantly increased in epileptic children compared with the control group. QTd was 58.1 +/- 13.4 ms and 35.9 +/- 9.3 ms and QTcd was 91.0 +/- 22.9 and 68.6 +/- 18.0ms in patients and controls, respectively. Antiepileptic treatment did not affect QT dispersion.</AbstractText>QT dispersion is increased in epileptic children. Further investigation is needed to reveal the pathogenesis of myocardial repolarization abnormalities in epileptic patients.</AbstractText> |
2,228 | Metabolically controlled reperfusion in acute myocardial infarction: should the polarizing solution be given subselectively? | In working rat hearts, metabolic support of injured tissue enhances recovery after acute myocardial infarction. Clinical experience with a systemic "polarizing solution" supports this claim.</AbstractText>In a dog model of ischemia/reperfusion, we tested the feasibility of subselectively supplying adapted metabolic substrates before instituting blood reperfusion.</AbstractText>Thirty-five dogs underwent ligation of the proximal left anterior descending artery and collaterals for 90 minutes. The animals were randomly assigned to receive direct blood reperfusion (Group I), intracoronary glucose, insulin, and potassium (Group II), or intracoronary glucose, insulin, and potassium plus propionyl-L-carnitine (PLC) (Group III). After 30 minutes of artificial reperfusion, prograde blood flow was resumed in groups II and III. A routine necropsy was performed 3 to 5 days later. Primary endpoints were severe arrhythmias, death, markers of infarct size, and specific histologic features.</AbstractText>We excluded 4 dogs for technical reasons and 2 others for preexisting cardiomyopathy. In the remaining 29 animals, large apical infarctions were documented ventriculographically during arterial ligation. One dog died of irreversible ventricular fibrillation during the initial ischemic period, and 9/28 dogs (32.1%) died during early reperfusion. Ventricular fibrillation was more common with 10% (versus 5%) dextrose concentrations and was eliminated by PLC. Irreversibly injured (versus jeopardized) areas of myocardium were more common in Group III (85.9 19.3%) than in Groups I and II (16.9 10.8%).</AbstractText>Subselective infusion of metabolically supportive solutions during acute myocardial infarction is technically feasible. To prevent osmotic endothelial damage, the perfusate must have a low (< 5%) dextrose content.</AbstractText> |
2,229 | Dual AV nodal pathways and conduction during atrial fibrillation. | AV node modification reduces ventricular rate during atrial fibrillation (AF). We induced AF in patients with dual AV nodal pathways before and after radiofrequency ablation (RFA) of AV nodal reentry tachycardia (AVNRT) and examined the role of the two pathways in the transmission of impulses during AF.</AbstractText>AF was induced in 30 patients before and after slow pathway ablation. Before RFA mean (AF CLmean) and shortest (AF CLshort) ventricular cycle lengths correlated significantly to ERPf, ERPs, and antegrade Wenckebach block (r = 0.53-0.67). Ablation eliminated slow pathway conduction completely in 10 patients (group A), whereas in 20 patients some slow pathway conduction was still present (group B). After RFA there was a 10% increase in AF CLmean (20%, p < 0.05 in A and 5%, p = NS in B) and 7% in AF CLshort (11%, p = NS in A and 6%, p = NS in B). During isoproterenol infusion after RFA AF CLmean increased 8% (p < 0.05) (14% in A and 6% in B; p < 0.05 in both groups). The effects of RFA were mainly confined to patients with ERPs less than the median value (13% vs 3% in those above median, respectively; p < 0.05).</AbstractText>The refractory periods of the AV nodal pathways are the main determinants of ventricular rate during induced AF. Slow pathway ablation reduces ventricular rate during AF. This effect was greatest when slow pathway conduction was completely eliminated. A short ERPs predicted a greater reduction in ventricular rate.</AbstractText> |
2,230 | Effect of losartan on sudden cardiac death in people with diabetes: data from the LIFE study. | In the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study, a major reduction of all-cause mortality--especially cardiovascular mortality--in patients with diabetes with left ventricular hypertrophy was reported for treatment with losartan. We postulated post hoc that losartan might have a better effect on sudden cardiac death than atenolol, and we aimed to test this hypothesis. 44 patients with diabetes died of sudden cardiac death; significantly fewer deaths arose in the losartan group (14) than in the atenolol group (30; p=0.027). In the losartan group, five (6%) of 86 patients with diabetes and atrial fibrillation during the trial died of sudden cardiac death compared with nine (2%) of 500 in those without atrial fibrillation. The respective figures for the atenolol group were 14 (13%) of 105 and 16 (3%) of 504. Our results suggest losartan affords better protection against cardiac death from arrhythmias for patients with diabetes mellitus than does atenolol. Importantly, our analyses were exploratory and require confirmation. |
2,231 | The effect of QRS cancellation on atrial fibrillatory wave signal characteristics in the surface electrocardiogram. | QRS cancellation methods have been used to analyze atrial activity in the electrocardiogram for such rhythms as atrioventricular dissociated ventricular tachycardia and atrial fibrillation. However, how well the cancellation methods work has never been evaluated by some gold standard. In this study of patients undergoing radiofrequency ablation of the atrioventricular junction, the contribution of imperfect cancellation was evaluated by comparing the "pure" atrial fibrillation (the gold standard) during a brief ventricular asystole to data obtained by a cancellation method during pacing just before and after the asystole. The results were compared by linear regression. The peak frequencies were 4.8-7.3 (6.1 +/- 0.8) Hz for the "pure" and 4.8-6.8 (5.9 +/- 0.7) Hz for the cancelled electrocardiogram segments (R(2) = 0.89) (similar results for median frequency), and the mean short-time Fourier transform peak frequencies were 4.6-7.1 (5.9 +/- 0.8) Hz for the "pure" and 4.7-6.8 (5.9 +/- 0.7) Hz for the cancelled segments (R(2) = 0.96). Further comparison was accomplished using synthesized signals. Based on our study, the cancellation method is reliable for studying atrial fibrillatory wave characteristics. As reported previously, the peak frequency and most power for atrial fibrillation in humans are in the 4-9 Hz band. |
2,232 | [Incidental diagnosis of an ostium-secundum-type interatrial communication during coronary surgery]. | Preoperative assessment of a 73-year-old woman scheduled for coronary revascularization revealed signs of severe disease in three coronary vessels, mild mitral valve insufficiency, moderate tricuspid insufficiency and moderate-to-severe pulmonary hypertension, with preserved left ventricular function. During surgery pulmonary artery catheter measurements confirmed pulmonary hypertension and the presence of very high cardiac output, leading to suspicion of atrial septal defect. Peripheral vein and right atrial blood samples revealed a sudden increase of 23 mm Hg in PO2 and of 22% in oxygen saturation. Finding the opening in the wall of the right atrium gave diagnostic confirmation of an ostium secundum defect 3 cm in diameter. The defect was closed and the coronary vessel bypasses were created. Upon weaning from extracorporeal circulation, the sudden oximetric increase was seen to have disappeared and pulmonary artery pressures had decreased. Postoperative course was satisfactory, with normal sinus rhythms alternating with episodes of atrial fibrillation. We stress the importance of invasive hemodynamic monitoring and transesophageal echography during heart surgery to confirm diagnoses that have not been established during preoperative assessment. |
2,233 | A fatal case considered to be due to cardiac arrhythmia associated with butane inhalation. | An autopsy case of a 14-year-old boy whose death is considered to be a result of cardiac arrhythmia after butane inhalation and sample preservation for butane analysis are reported. The electrocardiogram taken in the ambulance revealed ventricular fibrillation. There were no autopsy findings as to the cause of death. n-Butane, isobutane and propane were identified in the blood, brain and lung of the cadaver by headspace gas chromatography. Based on these results, the cause of death was concluded to be cardiac arrhythmia due to butane inhalation. As a follow-up, n-butane, isobutane and propane concentrations in the blood kept at -30 degrees C showed the unchanged values with a coefficient of variation of within 10% for 2 weeks. |
2,234 | Can P wave parameters obtained from 12-lead surface electrocardiogram be a predictor for atrial fibrillation in patients who have structural heart disease? | This study was planned to investigate the parameters detecting risk of developing atrial fibrillation (AF) in patients with sinus rhythm with structural heart disease. Forty-five patients with AF and 37 patients without AF but with structural heart disease (Group I) were included in this study. Thirty-eight patients (Group II) had successfully undergone medically or electrically cardioversion after transesophageal echocardiography. The restoration of sinus rhythm could not be achieved in 7 patients who were excluded from this study. After providing sinus rhythm, amiodarone was given orally to the patients to prevent recurrences. Left ventricular ejection fraction (LVEF) was calculated and left atrial diameter (LAD) was measured by echocardiography in group I and in group II after cardioversion. A 12-lead electrocardiography (ECG) was simultaneously obtained from all the patients. In these ECG recordings, maximum P wave duration (P max), minimum P wave duration (P min), and P wave dispersion (P dispersion) were calculated. P dispersion was expressed as "P max-P min." Also, the highest P wave voltage is expressed as P amplitude maximum (P amp max), the lowest P wave as P amplitude minimum (P amp min), and P amplitude dispersion (P amp dispersion) was calculated as the difference of both. In univariate analysis, P max, P dispersion, P amp max, P amp dispersion, LAD, LVEF, and old age were significant predictors of chronic AF (p < 0.001, p < 0.01, p < 0.01, p < 0.01, p = 0.003, p = 0.02, and p = 0.01, respectively). However, in multivariate analysis, P max and LAD were independent predictors of chronic AF in patients with structural heart disease (r = 0.39, p < 0.05; r = 0.34; p < 0.05, respectively). In conclusion, in estimating the risk of developing chronic AF, P max and LAD are predictive parameters in patients with sinus rhythm with structural heart disease. |
2,235 | Successful resuscitation after ropivacaine-induced ventricular fibrillation. | Human data about resuscitation after cardiac arrest from ropivacaine are limited. We present a case of successful cardiopulmonary resuscitation after accidental ropivacaine-induced ventricular fibrillation. A 76-yr-old female patient presented for foot osteotomy. A femoral block was performed using a nerve stimulator, a short bevel needle and 20 mL of 1.5% mepivacaine with 1:400,000 epinephrine. The patient remained relaxed and conversant. Five minutes later, an anterior sciatic block was done with 0.5% ropivacaine with 1:400,000 epinephrine for prolonged analgesia. Despite a negative aspiration and incremental injection, the patient developed a tonic-clonic seizure, then gradual widening of the QRS complex, and subsequently ventricular fibrillation. The patient was resuscitated with chest compressions and airway support prior to pharmacologic treatment of defibrillation. Total venous ropivacaine concentration 5 min after the last injection was 3.2 mg/L, free ropivacaine was 0.5 mg/L, and total mepivacaine was 0.22 mg/L. The patient was admitted to the hospital and discharged the next morning without complications. This case demonstrates that techniques used to detect intravascular injection may reduce but not eliminate catastrophic events. Consequently, regional anesthesia using large amounts of local anesthetic should be done in locations with resuscitation equipment and by individuals trained to recognize these complications and begin early treatment. |
2,236 | A randomized comparison of atrial and dual-chamber pacing in 177 consecutive patients with sick sinus syndrome: echocardiographic and clinical outcome. | A randomized trial was done to compare single-chamber atrial (AAI) and dual-chamber (DDD) pacing in patients with sick sinus syndrome (SSS). Primary end points were changes in left atrial (LA) size and left ventricular (LV) size and function as measured by M-mode echocardiography.</AbstractText>In patients with SSS and normal atrioventricular conduction, it is still not clear whether the optimal pacing mode is AAI or DDD pacing.</AbstractText>A total of 177 consecutive patients (mean age 74 +/- 9 years, 73 men) were randomized to treatment with one of three rate-adaptive (R) pacemakers: AAIR (n = 54), DDDR with a short atrioventricular delay (n = 60) (DDDR-s), or DDDR with a fixed long atrioventricular delay (n = 63) (DDDR-l). Before pacemaker implantation and at each follow-up, M-mode echocardiography was done to measure LA and LV diameters. Left ventricular fractional shortening (LVFS) was calculated. Analysis was on an intention-to-treat basis.</AbstractText>Mean follow-up was 2.9 +/- 1.1 years. In the AAIR group, no significant changes were observed in LA or LV diameters or LVFS from baseline to last follow-up. In both DDDR groups, LA diameter increased significantly (p < 0.05), and in the DDDR-s group, LVFS decreased significantly (p < 0.01). Atrial fibrillation was significantly less common in the AAIR group, 7.4% versus 23.3% in the DDDR-s group versus 17.5% in the DDDR-l group (p = 0.03, log-rank test). Mortality, thromboembolism, and congestive heart failure did not differ between groups.</AbstractText>During a mean follow-up of 2.9 +/- 1.1 years, DDDR pacing causes increased LA diameter, and DDDR pacing with a short atrioventricular delay also causes decreased LVFS. No changes occur in LA or LV diameters or LVFS during AAIR pacing. Atrial fibrillation is significantly less common during AAIR pacing.</AbstractText> |
2,237 | Cardioverter defibrillator implantation in a pregnant woman guided with transesophageal echocardiography. | This report describes a 28-year-old pregnant woman with mitral valve prolapse and sudden cardiac death due to a ventricular fibrillation who underwent an ICD implantation guided by tranesophageal echocardiography. |
2,238 | Intravenous administration of class I antiarrhythmic drug induced T wave alternans in an asymptomatic Brugada syndrome patient. | A 53-year-old man with an abnormal ECG was referred to the Nihon University School of Medicine. The 12-lead ECG showed right bundle branch block and saddleback-type ST elevation in leads V1-V3 (Brugada-type ECG). Signal-averaged ECG showed positive late potentials. Double ventricular extrastimuli (S1: 500 ms, S2: 250 ms, S3: 210 ms) induced VF. Amiodarone (200 mg/day) was administered for 6 months and programmed ventricular stimulation was repeated. VF was induced again by double ventricular stimuli (S1: 600 ms, S2: 240 ms, S3: 170 ms). Intravenous administration of class Ic antiarrhythmic drug, pilsicainide (1 mg/kg), augmented ST-T elevation in leads V1-V3, and visible ST-T alternans that was enhanced by atrial pacing was observed in leads V2 and V3. Visible ST-T wave alternans disappeared in 15 minutes. However, microvolt T wave alternans was present during atrial pacing at a rate of 70/min without visible ST-T alternans. |
2,239 | Adaptive pacing during ventricular fibrillation. | While it has been shown that pacing during ventricular fibrillation (VF) can capture a portion of the epicardium, little is known about the characteristics of the area captured or about whether adaptively changing the pacing rate during VF will increase the area captured. In six open-chested pigs, pacing during VF was performed from the center of a plaque containing 504 electrodes 2 mm apart in a21 x 24 array on the anterior right ventricle. Simultaneous recordings from the 504 electrodes were used to construct activation maps from which the area of epicardium captured by pacing was determined. Four pacing algorithms were examined: (1) fixed rate pacing at 95% of the median VF activation rate, (2 and 3) adaptive pacing in which the pacing timing and/or rate is reset in real time if capture is not obtained, and (4) pacing at a slowly increasing rate after initial capture. Regional capture, defined as control of the myocardium under at least 10 plaque electrodes, was achieved in 71% (92/129) of pacing episodes. The incidence of capture was not significantly different for pacing algorithms 1-3. The maximum area captured for each pacing episode with algorithms 1-3 was 3.8 +/- 2.0 cm2(mean +/- SD). Within each animal, the pattern of capture was similar among all pacing episodes, no matter which algorithm was use dr = 0.85 +/- 0.25). The region of greatest capture extended away from the pacing site along the long axis of the myocardial fibers. However, the area of captured epicardium toward the right ventricular side of the pacing electrode was 9.7 times greater than toward the left ventricular side. This principal direction toward the right ventricular side of the pacing electrode was the same direction traveled by the majority of VF activation fronts before capture occurred. The absence of recorded activations at the pacing site for 20 consecutive stimuli predicted 83% of the time that regional capture was present. With algorithm 4, the pacing rate could be increased 7.1%+/- 4.3%while maintaining capture; however, the area of capture progressively decreased as the pacing rate increased. While pacing from the anterior right ventricular epicardium during VF, the area of capture is repeatable and is markedly asymmetrical with almost 10 times as much epicardium captured on the side of the pacing electrode closest to the acute margin of the right ventricle as on the opposite side. This marked asymmetry is associated both with myofiber orientation and with the direction of spread of activation and hence the direction of dispersion of refractoriness during VF just before pacing is initiated. It is possible to perform adaptive pacing algorithms in real time during VF; however, the two adaptive algorithms tested did not capture significantly more epicardium than a simple fixed-rate pacing algorithm. Although it is possible to maintain capture while increasing the pacing rate during VF, the area of capture decreases. |
2,240 | Incessant nonreentrant tachycardia due to simultaneous conduction over dual atrioventricular nodal pathways mimicking atrial fibrillation in patients referred for pulmonary vein isolation. | It has been reported that conduction over the fast and slow pathways of the AV node can occur simultaneously, leading to a double ventricular response from each atrial beat. We report the cases of two patients referred to us for evaluation of symptomatic, incessant, and irregular narrow-complex tachycardia, misdiagnosed as atrial fibrillation, for consideration of pulmonary vein isolation. At presentation, careful evaluation of the electrograms revealed the presence of two ventricular activations for each atrial beat. At electrophysiologic study, both patients were found to have nonreentrant tachycardias arising from simultaneous conduction over the fast and slow pathways of the AV node. In one patient, the tachycardia had resulted in cardiomyopathy. Slow AV nodal pathway ablation performed in both patients resulted in cure of their tachycardias and recovery of ventricular function in the patient with cardiomyopathy. |
2,241 | Discrepancies between the upper limit of vulnerability and defibrillation threshold: prevalence and clinical predictors. | Upper limit of vulnerability (ULV) has a strong correlation with defibrillation threshold (DFT) in patients with implantable cardioverter defibrillators (ICDs). Significant discrepancies between ULV and DFT are infrequent. The aim of this study was to characterize patients with such discrepancies.</AbstractText>The ULV and DFT were determined in 167 ICD patients. Univariate and multivariate analyses were used to evaluate clinical predictors of a significant difference (> or =10 J) between ULV and DFT. Only 8 patients (5%) had > or =10 J difference. ULV exceeded DFT in all of them. Absence of coronary artery disease (6/8 vs 48/159 patients; P = 0.05) and absence of documented ventricular arrhythmias (4/8 vs 12/159 patients; P = 0.01) were the only independent predictors of a significant ULV-DFT discrepancy.</AbstractText>Significant discrepancies between ULV and DFT occur in 5% of patients with ICDs. Absence of coronary disease and documented ventricular arrhythmias predict such a discrepancy. At ICD implant, DFT testing is recommended in these patients and in patients with a high (>20 J) ULV before first-shock energy and the need for lead repositioning are determined.</AbstractText> |
2,242 | Ambulatory electrocardiogram-based tracking of T wave alternans in postmyocardial infarction patients to assess risk of cardiac arrest or arrhythmic death. | This is the first study to assess T wave alternans (TWA) analyzed from routine ambulatory electrocardiograms (AECGs) to identify postmyocardial infarction (post-MI) patients at increased risk for arrhythmic events.</AbstractText>The new method of modified moving average (MMA) analysis was used to measure TWA magnitude in 24-hour AECGs from ATRAMI, a prospective study of 1,284 post-MI patients. Using a nested case-control approach, we defined cases as patients who experienced cardiac arrest due to documented ventricular fibrillation or arrhythmic death during the follow-up period of 21 +/- 8 months. We analyzed 15 cases and 29 controls matched for sex, age, site of MI, left ventricular ejection fraction, thrombolysis, and beta-blockade therapy. TWA was reported as the maximum 15-second value at three predetermined times associated with cardiovascular stress: maximum heart rate, 8:00 A.M., and maximum ST segment deviation. TWA increased significantly from baseline in both leads at each time point (P <<0.01) in cases and controls. TWA in V5 increased more in cases than controls during peak heart rate (P = 0.005) and at 8:00 A.M. (P = 0.02). A 4- to 7-fold higher odds of life-threatening arrhythmias was predicted by TWA level above the 75th percentile during maximum heart rate in leads V1 (odds ratio [OR] 4.2, 95% confidence interval [CI]: 1.1-16.3, P = 0.04) and V5 (OR 7.9, 95% CI: 1.9-33.1, P = 0.005). TWA at 8:00 A.M. also predicted risk in leads V1 (OR = 5.0, 95% CI: 1.2-20.5, P = 0.02) and V5 (OR = 4.2, 95% CI: 1.1-16.3, P = 0.04).</AbstractText>TWA measurement from routine 24-hour AECGs is a promising approach for risk stratification for cardiac arrest and arrhythmic death in relatively low-risk post-MI patients.</AbstractText> |
2,243 | Short QT Syndrome: a familial cause of sudden death. | A prolonged QT interval is associated with a risk for life-threatening events. However, little is known about prognostic implications of the reverse-a short QT interval. Several members of 2 different families were referred for syncope, palpitations, and resuscitated cardiac arrest in the presence of a positive family history for sudden cardiac death. Autopsy did not reveal any structural heart disease. All patients had a constantly and uniformly short QT interval at ECG.</AbstractText>Six patients from both families were submitted to extensive noninvasive and invasive work-up, including serial resting ECGs, echocardiogram, cardiac MRI, exercise testing, Holter ECG, and signal-averaged ECG. Four of 6 patients underwent electrophysiological evaluation including programmed ventricular stimulation. In all subjects, a structural heart disease was excluded. At baseline ECG, all patients exhibited a QT interval <or=280 ms (QTc <or=300 ms). During electrophysiological study, short atrial and ventricular refractory periods were documented in all and increased ventricular vulnerability to fibrillation in 3 of 4 patients.</AbstractText>The short QT syndrome is characterized by familial sudden death, short refractory periods, and inducible ventricular fibrillation. It is important to recognize this ECG pattern because it is related to a high risk of sudden death in young, otherwise healthy subjects.</AbstractText> |
2,244 | Mapping and ablation of ventricular fibrillation associated with long-QT and Brugada syndromes. | The long-QT and Brugada syndromes are important substrates of malignant ventricular arrhythmia. The feasibility of mapping and ablation of ventricular arrhythmias in these conditions has not been reported.</AbstractText>Seven patients (4 men; age, 38+/-7 years; 4 with long-QT and 3 with Brugada syndrome) with episodes of ventricular fibrillation or polymorphic ventricular tachycardia and frequent isolated or repetitive premature beats were studied. These premature beats were observed to trigger ventricular arrhythmias and were localized by mapping the earliest endocardial activity. In 4 patients, premature beats originated from the peripheral right (1 Brugada) or left (3 long-QT) Purkinje conducting system and were associated with variable Purkinje-to-muscle conduction times (30 to 110 ms). In the remaining 3 patients, premature beats originated from the right ventricular outflow tract, being 25 to 40 ms ahead of the QRS. The accuracy of mapping was confirmed by acute elimination of premature beats after 12+/-6 minutes of radiofrequency applications. During a follow-up of 17+/-17 months using ambulatory monitoring and defibrillator memory interrogation, no patients had recurrence of symptomatic ventricular arrhythmia but 1 had persistent premature beats.</AbstractText>Triggers from the Purkinje arborization or the right ventricular outflow tract have a crucial role in initiating ventricular fibrillation associated with the long-QT and Brugada syndromes. These can be eliminated by focal radiofrequency ablation.</AbstractText> |
2,245 | Sudden arrhythmia death syndrome: importance of the long QT syndrome. | In approximately 5 percent of sudden cardiac deaths, no demonstrable anatomic abnormality is found. Some cases are caused by sudden arrhythmia death syndrome. A prolonged QT interval is a common thread among the various entities associated with sudden arrhythmia death syndrome. A number of drugs are known to cause QT prolongation (e.g., terfenadine), as are hypokalemia, hypomagnesemia, myocarditis, and endocrine and nutritional disorders. Recently, attention has focused on a group of inherited gene mutations in cardiac ion channels that cause long QT syndrome and carry an increased risk for sudden death. Some of the highest rates of inherited long QT syndrome occur in Southeast Asian and Pacific Rim countries. The median age of persons who die of long QT syndrome is 32 years; men are predominately affected. In addition to a prolonged QT interval, which occurs in some but not all persons with long QT syndrome, another characteristic electrocardiographic abnormality is the so-called Brugada sign (an upward deflection of the terminal portion of the QRS complex). Most cardiac events are precipitated by vigorous exercise or emotional stress, but they also can occur during sleep. Torsades de pointes and ventricular fibrillation are the usual fatal arrhythmias. Long QT syndrome should be suspected in patients with recurrent syncope during exertion and those with family histories of sudden, unexpected death. Unfortunately, not all persons with long QT syndrome have premonitory symptoms or identifiable electrocardiographic abnormalities, and they may first present with sudden death. Beta blockers, potassium supplements, and implantable defibrillators have been used for treatment of long QT syndrome. Identifying the specific gene mutation in a given patient with long QT syndrome can help guide prophylactic therapy. |
2,246 | Ablate and pace revisited: long term survival and predictors of permanent atrial fibrillation. | To assess long term mortality and identify factors associated with the development of permanent atrial fibrillation after atrioventricular (AV) node ablation for drug refractory paroxysmal atrial fibrillation.</AbstractText>Retrospective cohort study.</AbstractText>UK tertiary centre teaching hospital.</AbstractText>Patients admitted to the University Hospital Birmingham between January 1995 and December 2000.</AbstractText>AV node ablation and dual chamber mode switching pacing.</AbstractText>Long term mortality and predictors of permanent atrial fibrillation, assessed through Kaplan-Meier curves and logistic regression.</AbstractText>114 patients (1995-2000) were included: age (mean (SD)), 65 (9) years; 55 (48%) male; left atrial diameter 4 (1) cm; left ventricular end diastolic diameter 5 (1) cm; ejection fraction 54 (17)%. Indications for AV node ablation were paroxysmal atrial fibrillation in 95 (83%) and paroxysmal atrial fibrillation/flutter in 19 (17%). The survival curve showed a low overall mortality after 72 months (10.5%). Fifty two per cent of patients progressed to permanent atrial fibrillation within 72 months. There was no difference in progression to permanency between paroxysmal atrial fibrillation and paroxysmal atrial fibrillation/flutter (log rank 0.06, p = 0.8). Logistic regression did not show any association between the variables collected and the development of permanent atrial fibrillation, although age over 80 years showed a trend (p = 0.07).</AbstractText>Ablate and pace is associated with a low overall mortality. No predictors of permanent atrial fibrillation were identified, but 48% of patients were still in sinus rhythm at 72 months. These results support the use of dual chamber pacing for paroxysmal atrial fibrillation patients after ablate and pace.</AbstractText> |
2,247 | Proportion and prognosis of healthy people with coved or saddle-back type ST segment elevation in the right precordial leads during 10 years follow-up. | The aim of this study was to investigate long-term proportion and prognosis of healthy subjects with right precordial ST segment elevation without family history of sudden death.</AbstractText>We followed up electrocardiograms (ECGs) of 3339 healthy subjects (male/female 2646/693) who underwent periodical medical examination form 1992 to 2001 to determine the relationship between year-to-year changes of ST segment morphology and the risk of fatal arrhythmias. Inclusion criterion was defined as presenting either coved or saddle back type ST segment elevation (>0.2 mV) in the right precordial leads. The cumulative total subjects who showed Brugada-like ECG changes at least once throughout the follow-up period were 69 (male/female 67/2; age 47.9+/-8.9 years, 2.1% of total subjects). During a follow-up period, annual mean proportion of coved or saddle back type ST elevation in the right precordial leads was 1.22+/-0.23% (0.88-1.88%). The morphological pattern of ST segment elevation was saddle-back in 77.3+/-7.9% and coved in 22.7+/-7.9% of subjects. Throughout the follow-up period, 39 subjects (56.5%) showed changes in ST segment elevation pattern. Twenty-nine subjects (42.0%) showed normalization of ST segment elevation at least once. Sixty-nine subjects were followed for a period of one to 10 years (median 4 years, interquartile range 4-8 years). Only one subject with persistent saddle-back type ST elevation had episodes of ventricular fibrillation (VF).</AbstractText>The average proportion of healthy subject who had coved or saddle-back type of ST elevation in the right precordial leads without family history of sudden death was 1.22% and the risk of fatal arrhythmias was low (1/393.5 subject-years).</AbstractText> |
2,248 | High prevalence of right ventricular involvement in endurance athletes with ventricular arrhythmias. Role of an electrophysiologic study in risk stratification. | Electrocardiographic abnormalities and premature ventricular contractions are common in athletes and are generally benign. However, the specific outcome of high-level endurance athletes with frequent and complex ventricular arrhythmias is unclear. Also, information on the predictive accuracy of different investigations in this subgroup is unknown.</AbstractText>We report on 46 high-level endurance athletes with ventricular arrhythmias (45 male; median age 31 years) followed-up for a median of 4.7 years. Eighty percent were cyclists. Hypertrophic cardiomyopathy or coronary abnormalities were present in < or =5%. Eighty percent of the arrhythmias had a left bundle branch morphology. Right ventricular (RV) arrhythmogenic involvement (based on a combination of multiple criteria) was manifest in 59% of the athletes, and suggestive in another 30%. Eighteen athletes developed a major arrhythmic event (sudden death in nine, all cyclists). They were significantly younger than those without event (median 23 years vs 38 years; P=0.01). Outcome could not be predicted by presenting symptoms, non-invasive arrhythmia evaluation or morphological findings at baseline. Only the induction of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) during invasive electrophysiological testing was significantly related to outcome (RR 3.4; P=0.02). Focal arrhythmias were associated with a better prognosis than those due to reentry (P=0.02) but the mechanism could be determined in only 22 (48%).</AbstractText>Complex ventricular arrhythmias do not necessarily represent a benign finding in endurance athletes. An electrophysiological study is indicated for risk evaluation, both by defining inducibility and identifying the arrhythmogenic mechanism. Endurance athletes with arrhythmias have a high prevalence of right ventricular structural and/or arrhythmic involvement. Endurance sports seems to be related to the development and/or progression of the underlying arrhythmogenic substrate.</AbstractText> |
2,249 | Residual flow to the infarct zone against lethal ventricular tachyarrhythmias during the acute phase of myocardial infarction. | The benefits of residual flow to the infarct zone have been demonstrated in acute myocardial infarction (AMI), but its relation to ventricular tachyarrhythmias remains uncertain.</AbstractText>This study was undertaken to test the hypothesis that residual flow is an important determinant of lethal ventricular tachyarrhythmias (sustained ventricular tachycardia or ventricular fibrillation) during the acute phase of AMI.</AbstractText>We investigated the determinants of lethal ventricular tachyarrhythmias within 24 h after the onset of symptoms in 310 consecutive patients (256 men; age 57.4 +/- 11.5 years) with AMI undergoing primary angioplasty. Patients were divided into two groups: those with (Group 1, n = 40) and those without (Group 2, n = 270) lethal ventricular tachyarrhythmias. Residual flow was defined as the presence of anterograde flow (> or = Thrombolysis in Myocardial Infarction [TIMI] 2 flow) or good angiographic collaterals (> or = grade 2) on a preintervention angiogram.</AbstractText>Univariate determinants of lethal ventricular tachyarrhythmias were cardiogenic shock, systolic blood pressure, peak level of creatine kinase, culprit artery, spontaneous reperfusion, and residual flow. In multivariate analysis, however, cardiogenic shock (odds ratio [OR] = 4.79, 95% confidence interval [CI] 1.63-14.11, p = 0.004), residual flow (OR = 0.34, 95% CI 0.14-0.81, p = 0.015), and the right coronary artery as the culprit artery (OR = 2.09,95% CI 1.03-4.22, p = 0.040) were independent determinants of these arrhythmias. In-hospital death occurred in 10 patients and was more common in Group 1 than in Group 2 (12.5% vs. 1.9%, respectively, p < 0.001).</AbstractText>The absence of residual flow was associated with greater risk of lethal ventricular tachyarrhythmias during the acute phase of AMI, suggesting a protective role of residual flow against these arrhythmias in AMI.</AbstractText> |
2,250 | Implantable defibrillator therapy. | Sudden cardiac death (SCD) is the most important cause of death in the industrialised world. Treatment with antiarrhythmic drugs (AAD), however, proved disappointing in preventing SCD. From drugs with electrophysiological properties, only treatment with beta-blockers has been shown to improve clinical outcome. This lack of efficiency of AADs heralded a new era of secondary and primary prevention trials, comparing implantable cardioverterdefibrillator (ICD) with drug therapy. Three large randomised secondary prevention trials were conducted in patients with prior myocardial infarction who where resuscitated from VT or VF. Meta-analysis of these three studies show consistent ICD benefit. This ICD benefit is also observed in three large randomised primary prevention trials in patients with a prior myocardial infarction and left ventricular dysfunction. The beneficial effect of ICD therapy proves to be significantly more pronounced in patients with the lowest left ventricular ejection fraction (26-30%). In patients with nonischaemic dilated cardiomyopathy and low ejection fractions, however, currently the only evidence-based indication for ICD implantation is secondary prevention. |
2,251 | Advances in ablation therapy for complex arrhythmias: atrial fibrillation and ventricular tachycardia. | Catheter ablation has evolved over the past two decades to become first-line therapy for many cardiac arrhythmias. Multiple advances in the technology and understanding of radiofrequency ablation have allowed this technique to blossom into one of the most powerful therapeutic tools available to the electrophysiologist, and have opened a new chapter in the diagnosis and management of clinical arrhythmias. Catheter ablation often eliminates the need for chronic drug therapy and can result in significant long-term cost savings. As catheter technology continues to improve, and newer, more effective energy delivery systems are developed, the applicability of catheter-based therapy will continue to expand. This review addresses some of the more commonly encountered clinical arrhythmias and the recent developments in the treatment of these arrhythmias from a catheter-based standpoint. |
2,252 | Advances in the acute pharmacologic management of cardiac arrhythmias. | Safe and effective control of rapid ventricular rates in acute-onset atrial fibrillation (AF) can be accomplished with intravenous calcium antagonists, beta-blockers or amiodarone; digoxin is less effective. If pharmacologic cardioversion of AF is desired, single oral doses of propafenone or flecainide are safe and effective in patients without structural heart disease. Intravenous ibulitide is moderately effective in the conversion of persistent AF or atrial flutter, with a small risk of proarrhythmia. In wide QRS complex tachycardia of uncertain origin, adenosine and lidocaine are no longer recommended. Procainamide or amiodarone are the treatment options, but attempts should be made to define the origin of tachycardia. In the treatment of monomorphic ventricular tachycardia, lidocaine is no longer recommended; procainamide or amiodarone are the recommended therapies. In polymorphic ventricular tachycardia with a normal QT interval, beta-blockers are recommended. In shock-refractory ventricular fibrillation, lidocaine, and magnesium are ineffective; intravenous amiodarone should be the treatment of choice. |
2,253 | Pharmacologic management of atrial fibrillation in the elderly: rate control, rhythm control, and anticoagulation. | Atrial fibrillation (AF) is the most prevalent major arrhythmia in the elderly. It may lead to significant morbidity and mortality through both primary cardiac effects and thromboembolic complications. It is controversial how aggressive physicians should be in their efforts to maintain normal sinus rhythm. Clearly, elderly patients with hemodynamic impairment or other symptoms of AF should undergo attempts to convert AF and maintain normal sinus rhythm, by means of cardioversion and initiation of antiarrhythmic medications. In patients left in AF, rate control with atrioventricular nodal-slowing agents is appropriate. The use of anticoagulation in the elderly is often complicated by concerns about excessive bleeding or falls in this population; however, evidence strongly supports the need for anticoagulation with close monitoring even in the extreme elderly. Because of the high prevalence of asymptomatic AF and the high burden of thromboembolism in the elderly, even patients ostensibly maintained in normal sinus rhythm should continue systemic anticoagulation in the absence of contraindications. |
2,254 | New indications for pacing. | This article reviews developments in four areas: single- versus dual-chamber pacing, pacing for prevention of atrial fibrillation (AF), pacing for the treatment of neuromediated syncope, and pacing in patients with congestive heart failure. Large, randomized clinical trials comparing physiologic and ventricular pacing in different pacemaker populations have demonstrated that physiologic pacing does prevent AF but does not reduce cardiac mortality or stroke. The benefit for prevention of AF appears to be in patients with sinus node disease as the primary indication for pacing. Selective atrial pacing algorithms designed for the prevention of AF have not been shown to substantially reduce the overall burden of AF. Cardiac pacing has been shown to have a moderate benefit in the treatment of neuromediated syncope. Cardiac resynchronization therapy is emerging as a promising new treatment for heart failure. Long-term studies report that it improves quality of life and functional capacity, and reduces hospitalizations for heart failure. The impact of this therapy on mortality awaits the results of ongoing studies. |
2,255 | Frequency of ventricular fibrillation as predictor of one-year survival from out-of-hospital cardiac arrests. | This study determined whether electrocardiographic analysis of ventricular fibrillation (VF) can predict 1-year survival from bystander-witnessed, out-of-hospital cardiac arrests of cardiac origin. VF was analyzed using fast-Fourier transformation in a community in which emergency medical technicians delivered shock with an automated external defibrillator before arrival to the hospital. The frequency of VF can predict survival 1 year after hospital discharge from shock-delivered, bystander-witnessed cardiac arrests of cardiac etiology. |
2,256 | Mortality, morbidity, and complications in 3344 patients with implantable cardioverter defibrillators: results fron the German ICD Registry EURID. | ICDs are the therapy of choice in patients with life-threatening ventricular arrhythmias. Mortality, morbidity, and complication rates including appropriate and inappropriate therapies are unknown when ICDs are used in routine medical care and not in well-defined patients included in multicenter trials. Therefore, the data of 3,344 patients (61.1 +/- 12.1 years; 80.2% men; CAD 64.6%, dilated cardiomyopathy 18.9%; NYHA Class I-III: 19.1%, 54.3%, 20.1%, respectively; LVEF > 0.50: 0.234, LVEF 0.30-0.50: 0.472, LVEF < 0.30: 0.293, respectively) implanted in 62 German hospitals between January 1998 and October 2000 were prospectively collected and analyzed as a part of the European Registry of Implantable Defibrillators (EURID Germany). The 1-year survival rate was 93.5%. Patients in NYHA Class III and aLVEF < 0.30 had a lower survival rate than patients in NYHA Class I and a preserved LVEF (0.852 vs 0.975,P = 0.0001). Including the 1-year follow-up, 49.5% of patients had an intervention by the ICD, 39.8% had appropriate ICD therapies, 16.2% had inappropriate therapies. Overall, 1,691 hospital readmissions were recorded. The main causes for hospital readmissions were ventricular arrhythmias (61.3%) and congestive heart failure symptoms (12.9%). Thus, demographic data and mortality of patients treated with an ICD in conditions of standard medical care seems to be comparable and based on, or congruent with, the large secondary preventions trials. When ICDs are used in standard medical care, the 1-year survival rate is high, especially in patients with NYHA Class I and preserved LVEF. However, nearly half of all patients suffer from ICD intervention. |
2,257 | Electrophysiological features of orthodromic atrioventricular reentry tachycardia in patients with wolff-Parkinson-white syndrome and atrial fibrillation. | The aim of this study was to compare the electrophysiological features of tachycardia between WPW patients with and without AF. The study population consisted of 114 patients with WPW syndrome and reciprocating tachycardia during electrophysiological study. Two groups were selected: group I with AF during the procedure(n = 42)and the control group n = 72 without AF (group II). Cycle length (V-V interval), antero A-V, retrograde V-A conduction time during tachycardia and indexes V-A/V-V were analyzed. In addition, the relation between antero-, retrograde conduction time, and V-V was evaluated. Selection of the most predictive factor for AF presence was performed using regression analysis. Significant differences between the two groups were observed. These included a higher rate of tachycardia, shorter anterograde conduction time, A-V/V-V-indexes, longer retrograde conduction time, and V-A/V-V-indexes in group I compared with group II. Significant, positive correlations between anterograde conduction time and V-V were present in both groups, but retrograde conduction correlated significantly with the V-V-interval only in group II and group I (r = 0.37 vs r =-0.01, respectively). Significant, negative correlations between A-V and V-A conduction time in all analyzed points has been found to exist in group I (r =-0.45 for the point of maximal preexcitation [PMP]), whereas there were no significant correlations between these parameters in group II (r = 0.04). The most powerful AF predictor has been identified as the V-A/V-V index. The presence of AF in WPW syndrome may be associated with discrete patient characteristics. Ventricular activation occurs earlier, and atrial later, in the tachycardia cycle in AF than in patients free of AF. The different ability of the accessory pathway for adaptation to tachycardia rate changes in group I causes prolonged retrograde conduction over the pathway while the tachycardia rate increases. |
2,258 | Radiofrequency catheter ablation: different cooled and noncooled electrode systems induce specific lesion geometries and adverse effects profiles. | The success and safety of standard catheter radiofrequency ablation may be limited for ablation of atrial fibrillation and ventricular tachycardia. The aim of this study was to characterize and compare different cooled and noncooled catheter systems in terms of their specific lesion geometry, incidence of impedance rise, and crater and coagulum formation to facilitate appropriate catheter selection for special indications. The study investigated myocardial lesion generation of three cooled catheter systems (7 Fr, 4-mm tip): two saline irrigation catheters with a showerhead-type electrode tip (sprinkler) and a porous metal tip and an internally cooled catheter. Noncooled catheters (7 Fr) had a large tip electrode (8 mm) and a standard tip electrode (4 mm). RF energy was delivered on isolated porcine myocardium superfused with heparinized pig blood (37 degrees C) at power settings of 10-40 W. Both irrigated systems were characterized by a large lesion depth (8.1 +/- 1.6 mm) and a large lesion diameter (13.8 +/- 1.6 mm). In comparison, internally cooled lesions showed a similar lesion depth (8.0 +/- 1.0 mm), but a significantly smaller lesion diameter (12.3 +/- 1.2 mm,P = 0.04). Large tip lesions had a similar lesion diameter (14.5 +/- 1.6 mm), but a significantly smaller lesion depth (6.3 +/- 1.0 mm,P = 0.002) compared to irrigated lesions. However, lesion volume was not significantly different between the three cooled and the large tip catheter. To induce maximum lesion size, power requirements were three times higher for the irrigation systems and two times higher for the internally cooled and the large tip catheter compared to the standard catheter. Impedance rise was rarest with irrigated and large tip ablation. In case of impedance rise crater formation was a frequent observation (61-93%). Irrigated catheters prevented coagulum formation most effectively. Irrigated rather than internally cooled ablation appears to be most adequate for the induction of deep and long lesions at a low rate of impedance rise and thrombus formation. Large tip ablation may be feasible for the creation of long linear lesions, however, with an increased risk of thrombus formation. |
2,259 | Effect of two new PBN-derived phosphorylated nitrones against postischaemic ventricular dysrhythmias. | Spin traps might exert antioxidant cardioprotective effects during myocardial ischaemia-reperfusion where free radicals are thought to be responsible for the occurrence of reperfusion injury. The aim of our study was to investigate the effects of two new alpha-phenyl N-tert-butylnitrone (PBN)-derived beta-phosphorylated nitrones: 2-N-oxy-N-[benzylidène amino] diéthyl propyl-2-phosphate (PPN) and 1-diethoxyphosphoryl-1-methyl-N-[(1-oxido-pyridin-1-ium-4-yl) methylidene] ethylamine N-oxide (4-PyOPN) compared with PBN on (1) the evolution of cardiovascular parameters and (2) the postischaemic recovery. Anaesthetized rats were injected with 120 micro mol/kg of the nitrones or 14 micro mol/kg of amiodarone, used as a reference antidysrhythmic drug. Ischaemia was induced in vivo through ligation of the left anterior descending coronary artery for 5 min followed by 15 min of reperfusion after release. Cardiovascular parameters and occurrence of ventricular premature beats (VPB), ventricular tachycardia (VT) and fibrillation (VF) were recorded throughout the experiment. Under nonischaemic conditions, none of the three spin traps was shown to modify cardiovascular parameters during the 25-min measurement period. Solvent-treated (NaCl 0.9%) animals challenged with ischaemia-reperfusion exhibited 39 +/- 10 VPB, 156 +/- 39 s of VT and 60% mortality caused by sustained VF. Nitrones improved slightly postischaemic recovery, reducing the occurrence of VF and mortality to 33% whereas amiodarone injection totally suppressed rhythm disturbances and mortality. Our study has shown only limited antidysrhythmic cardioprotective effects of PBN-derived beta-phosphorylated nitrones during reperfusion after a regional myocardial ischaemia but also minor antioxidant properties of these spin trapping agents. |
2,260 | [A case of coronary artery spasm during epidural anesthesia with continuous infusion of propofol]. | A 50-year-old male patient was scheduled for left partial pulmonary resection and biopsy. The patient had neither complication nor history of ischemic heart disease. After arriving in the operation room, an epidural catheter was inserted into the epidural space at the T 4-5 intervertebral space. Anesthesia was induced with intravenous propofol 100 mg, fentanyl 100 microgram and vecuronium 6 mg and then a double lumen endotracheal tube was inserted. Anesthesia was maintained with O2 and air (FIO2 0.3-1.0), continuous infusion of propofol, intermittent intravenous administration of fentanyl and epidural injection of 1% lidocaine. Forty-five minutes after the start of operation, ECG showed an elevation of ST segment and soon it passed into ventricular tachycardia and ventricular fibrillation. The patient was treated with cardiopulmonary resuscitation. Fifteen minutes later, ECG returned to sinus rhythm but the elevation of ST segment remained. We considered that these cardiac events were due to coronary spasm, and started continuous infusion of nitroglycerin and nicorandil. One hour later, ST segment returned to normal. The possible inducing factors in this case were altered balance between sympathetic and parasympathetic nervous activity caused by infusion of propofol and epidural block, and alpha-stimulation caused by ephedrine. |
2,261 | [Suppression of frequent ventricular fibrillation attacks after induction of anesthesia with fentanyl, sevoflurane and propofol: a case report]. | We experienced emergency anesthetic management of a 51-year-old male for exchange of a battery in an implantable cardioverter defibrillator. He had repeated and intractable attacks of ventricular fibrillation (Vf) before induction of anesthesia. Infusion of propofol at 100 mg.hr-1 failed to suppress the Vf attacks in the ICU. However, the Vf attacks were suppressed by the addition of fentanyl 100 micrograms, nitrous oxide and sevoflurane to the infusion of propofol. It is speculated that general anesthetics inhibit Vf attacks by direct suppression of myocardium and reduction of sympathetic nervous activity. |
2,262 | [Hemodynamic collapse during off-pump coronary artery bypass grafting and optimization]. | The present study addressed the incidence of unpredicted hemodynamic collapse in off-pump coronary artery bypass grafting (OPCAB). Since 1999, OPCAB was attempted in 114 patients without preoperative hemodynamic collapse to date. 95% patients of OPCAB were completed without percutaneous cardiopulmonary support (PCPS) and all patients were discharged. In this study, patients are divided into a prophase of 60 patients and an anaphase of 50 patients, in consideration of learning curve. As for the trouble in procedures, 12 patients of ventricular fibrillation, 6 patients of conversion to PCPS, 19 patients of bradycardia which were evaded in temporary pacing were observed. Patients with conversion to PCPS decreased in 5 patients (8%) in prophase and 1 patient (1.8%) in anaphase. Avoidance of hemodynamic collapse were prevention of ischemia by positive use of coronary perfusion, prophylactic intra-aortic balloon pumping (IABP) use for decrease of blood pressure, apical evacuation heart positioner for visual field security. |
2,263 | Intestinal ischaemia during cardiac arrest and resuscitation: comparative analysis of extracellular metabolites by microdialysis. | Intestinal ischaemia is a major complication of shock syndromes causing translocation of bacteria and endotoxins and multiple organ failure in intensive care patients. The present study was designed to use microdialysis as a tool to monitor intestinal ischaemia after cardiac arrest and resuscitation in pigs. For this purpose, microdialysis probes were implanted in pig jejunal wall, peritoneum, skeletal muscle and brain, and interstitial fluid was obtained during circulatory arrest (induced by ventricular fibrillation) and after return of spontaneous circulation (ROSC). Cardiac arrest for 4 min caused a prolonged (60 min) reduction of blood flow in jejunal wall, muscle and brain as determined by the ethanol technique. This was accompanied by cellular damage in heart muscle and brain as indicated by increased levels of troponin-I and protein S-100, respectively. Plasma levels of glucose, lactate and choline were increased at 15-60 min following cardiac arrest. In contrast, cardiac arrest induced a rapid but variable decrease of interstitial glucose levels in all monitored organs; this decrease was followed by an increase over baseline during reperfusion. In the intestine, lactate, glutamate and choline levels were increased during ischaemia and reperfusion for 60-120 min; intestinal and peritoneal samples yielded parallel changes of lactate levels. Brain and muscle samples showed similar changes as in intestinum and peritoneum except for glutamate, which was increased in brain but not in muscle. We conclude that intestinal ischaemia occurs as a consequence of cardiac arrest and resuscitation and can be monitored by in vivo microdialysis. Comparative analysis by multi-site microdialysis reveals that the intestine is equally or even more sensitive to ischaemia than brain or muscle. |
2,264 | Effect of amiodarone on haemodynamics during cardiopulmonary resuscitation in a canine model of resistant ventricular fibrillation. | Amiodarone has been shown to be superior to both placebo and lidocaine in improving survival to hospital admission for victims of out-of-hospital refractory ventricular fibrillation. Concern had been expressed about the known vasodilatatory effects of amiodarone if given without precedent vasoconstrictive medications. The haemodynamic effects of intravenous amiodarone administered during ongoing CPR have not been systemically investigated. Our intention was to verify if amiodarone alone produced significantly lower resuscitation haemodynamics than did either adrenaline (epinephrine) alone or the combination of amiodarone and adrenaline.</AbstractText>Prospective, randomized, comparative study.</AbstractText>Research laboratory of a medical school.</AbstractText>Thirty mongrel dogs.</AbstractText>After 8 min of untreated VF, defibrillation was attempted once at 3 J/kg and external chest compressions and ventilation started. Those animals resistant to the defibrillation attempt were randomized, ten to an adrenaline (0.02 mg/kg) group, ten to an amiodarone (5 mg/kg) group, and ten to a group receiving a combination of both drugs.</AbstractText>Aortic systolic and diastolic, and coronary perfusion pressures were all significantly lower in the group receiving amiodarone alone than in the other two groups. Amiodarone combined with adrenaline produced pressures during CPR similar to adrenaline alone.</AbstractText>Amiodarone can be safely administered simultaneously in combination with adrenaline and such a combination results in similar haemodynamic support as adrenaline alone. Amiodarone administered alone produces significantly lower coronary perfusion pressure than when combined with adrenaline.</AbstractText> |
2,265 | Quality of CPR with three different ventilation:compression ratios. | Current adult basic cardiopulmonary resuscitation (CPR) guidelines recommend a 2:15 ventilation:compression ratio, while the optimal ratio is unknown. This study was designed to compare arterial and mixed venous blood gas changes and cerebral circulation and oxygen delivery with ventilation:compression ratios of 2:15, 2:50 and 5:50 in a model of basic CPR. Ventricular fibrillation (VF) was induced in 12 anaesthetised pigs, and satisfactory recordings were obtained from 9 of them. A non-intervention interval of 3 min was followed by CPR with pauses in compressions for ventilation with 17% oxygen and 4% carbon dioxide in a randomised, cross-over design with each method being used for 5 min. Pulmonary gas exchange was clearly superior with a ventilation:compression ratio of 2:15. While the arterial oxygen saturation stayed above 80% throughout CPR for 2:15, it dropped below 40% during part of the ventilation:compression cycle for both the other two ratios. On the other hand, the ratio 2:50 produced 30% more chest compressions per minute than either of the two other methods. This resulted in a mean carotid flow that was significantly higher with the ratio of 2:50 than with 5:50 while 2:15 was not significantly different from either. The mean cerebrocortical microcirculation was approximately 37% of pre-VF levels during compression cycles alone with no significant differences between the methods. The oxygen delivery to the brain was higher for the ratio of 2:15 than for either 5:50 or 2:50. In parallel the central venous oxygenation, which gives some indication of tissue oxygenation, was higher for the ratio of 2:15 than for both 5:50 and 2:50. As the compressions were done with a mechanical device with only 2-3 s pauses per ventilation, the data cannot be extrapolated to laypersons who have great variations in quality of CPR. However, it might seem reasonable to suggest that basic CPR by professionals should continue with ratio of 2:15 at present if it can be shown that similar brief pauses for ventilation can be achieved in clinical practice. |
2,266 | The epidemiology of cardiac arrest in children and young adults. | To describe the epidemiology of children and young adults suffering from out-of-hospital cardiac arrest.</AbstractText>All patients suffering from out-of-hospital cardiac arrest in whom, resuscitation efforts were attempted in the community of Göteborg between 1980 and 2000.</AbstractText>Between 31 October 1980 and 31 October 2000, all consecutive cases of cardiac arrest in which the emergency medical service (EMS) system responded and attempted resuscitation were reported and followed-up to discharge from hospital.</AbstractText>Among 5505 cardiac arrests information on age was available in 5290 cases (96%). Of these 5290 cases 98 (2%) were children (age 0-17 years), 197 (4%) were young adults (age 18-35 years) and the remaining 4995 (94%) were adults (age >35 years). Children and young adults differed from adults by suffering from a witnessed arrest less frequently, being found by the ambulance crew in ventricular fibrillation/tachycardia less frequently and being judged as having an underlying cardiac aetiology less frequently. Of the children only 5% were discharged from hospital alive compared with 8% for young adults and 9% for adults. Among survivors the cerebral performance categories (CPC) score at discharge tended to differ with 38% of young adults registering a CPC score of 1 (no neurological deficit) compared with 52% among adults.</AbstractText>Children and young adults suffering from out-of-hospital cardiac arrest differed from adults in terms of aetiology and observed initial arrhythmia. Children had a particularly bad outcome whereas young adults had a similar outcome as adults.</AbstractText> |
2,267 | Impact of rate versus rhythm control on quality of life in patients with persistent atrial fibrillation. Results from a prospective randomized study. | Despite the high prevalence of atrial fibrillation (AF), there are only limited data on quality of life (QoL) stemming from prospective trials comparing rate versus rhythm control. This prospective study evaluated QoL in patients with symptomatic persistent AF randomized to therapy aiming at rate versus rhythm control.</AbstractText>Patients with symptomatic persistent AF (7 to 360 days duration) were prospectively randomized to ventricular rate control (n=125) or to cardioversion and maintenance of sinus rhythm (n=127). QoL was assessed by the Medical Outcomes Study Short Form health survey (SF-36) at baseline and during 1 year of follow-up. Changes in QoL were compared on an intent-to-treat basis, and subsequently between patients in sinus rhythm versus AF. At baseline, all SF-36 scales were reduced compared to healthy controls. At 1 year, six of eight items had improved significantly in patients assigned to rate control, and five of eight items on rhythm control (p=ns). The physical component summary showed a comparable increase with both treatment strategies (rate control: p=0.004; rhythm control: p<0.001) whereas no significant changes were found for the mental component summary. At 1 year, 55% of patients reported a positive health transition with no inter-group differences. There were no significant differences in QoL in patients in sinus rhythm or AF at the end of the observation period.</AbstractText>In patients with symptomatic persistent AF, the two treatment strategies of rate versus rhythm control are associated with similar improvements in QoL.</AbstractText> |
2,268 | Quality of life in nonpharmacologic treatment of atrial fibrillation. | The mainstay of treatment for atrial fibrillation, AF, remains pharmacologic control, either by maintaining sinus rhythm or by controlling the ventricular rate and allowing AF to continue. In patients where pharmacologic therapy i not effective, not tolerated or contraindicated, nonpharmacologic treatment may be beneficial. In the last two decades the number of nonpharmacologic treatment options (catheter ablation, cardiac pacing, internal defibrillation, and dysrhythmia surgery) for AF have markedly increased and the number of patients undergoing such treatment is steadily increasing. The most important reason for these treatment strategies is the hope of reducing symptoms, preventing complications and improving quality of life, QoL. However, the impact of nonpharmacologic therapy on QoL is far from established. Following a short presentation of the basic definitions and instruments used in QoL research the present paper reviews clinical studies that have assessed QoL in patients undergoing nonpharmacologic treatment of AF. Major limitations and methodological problems are emphasized. Among these are highly selected often-heterogeneous patients groups, small size, lack of control group and the use of non-validated QoL instruments. Furthermore, in most studies antiarrhythmic medication have been discontinued at the time of the intervention and it is not clear to which degree the improvement in QoL is related solely to the nonpharmacologic treatment or to the removal of drug related adverse effects. Although the currently available data from adequately designed studies are sparse and further investigations are needed, it is noteworthy that the majority of patients undergoing nonpharmacologic treatment report enhanced QoL. |
2,269 | Characterization of the in vivo cardiac electrophysiologic effects of high-dose cocaine in closed-chest, anesthetized dogs with normal hearts. | To characterize the cardiac electrophysiologic effects of cocaine.</AbstractText>In 8 dogs (9-13 kg), electrophysiologic parameters and programmed stimulation were undertaken using transvenous catheters at baseline, and after cocaine intravenous infusion (12 mg/kg bolus followed by 0.22 mg/kg/min for 25 minutes).</AbstractText>Cocaine plasma levels (n=5) rose to 6.73 +/- 0.56 mg/mL. Cocaine did not affect sinus cycle length and arterial pressure. Cocaine prolonged P wave duration (54 +/- 6 vs 73 +/- 4 ms, P<0.001), PR interval (115 +/- 17 vs 164 +/- 15 ms, P<0.001), QRS duration (62 +/- 10 vs 88 +/- 14 ms, P<0.001), and QTc interval (344 +/- 28 vs 403 +/- 62 ms, P=0.03) but not JT interval (193 +/- 35 vs 226 +/- 53 ms, NS). Cocaine prolonged PA (9 +/- 6 vs 23 +/- 8 ms, P<0.001), AH (73 +/- 16 vs 92 +/- 15 ms; P=0.03), and HV (35 +/- 5 vs 45 +/- 3 ms; P<0.001) intervals and Wenckebach point (247 +/- 26 vs 280 +/- 28 ms, P=0.04). An increase occurred in atrial (138 +/- 8 vs 184 +/- 20 ms; P<0.001) and ventricular (160 +/- 15 vs 187 +/- 25 ms; P=0.03) refractoriness at a cycle length of 300 ms. Atrial arrhythmias were not induced in any dog. Ventricular fibrillation (VF) was induced in 2/8 dogs at baseline and 4/8 dogs after cocaine.</AbstractText>High doses of cocaine exert significant class I effects and seem to enhance inducibility of VF but not of atrial arrhythmias.</AbstractText> |
2,270 | Static filling pressure in patients during induced ventricular fibrillation. | The static pressure resulting after the cessation of flow is thought to reflect the filling of the cardiovascular system. In the past, static filling pressures or mean circulatory filling pressures have only been reported in experimental animals and in human corpses, respectively. We investigated arterial and central venous pressures in supine, anesthetized humans with longer fibrillation/defibrillation sequences (FDSs) during cardioverter/defibrillator implantation. In 82 patients, the average number of FDSs was 4 +/- 2 (mean +/- SD), and their duration was 13 +/- 2 s. In a total of 323 FDSs, arterial blood pressure decreased with a time constant of 2.9 +/- 1.0 s from 77.5 +/- 34.4 to 24.2 +/- 5.3 mmHg. Central venous pressure increased with a time constant of 3.6 +/- 1.3 s from 7.5 +/- 5.2 to 11.0 +/- 5.4 mmHg (36 points, 141 FDS). The average arteriocentral venous blood pressure difference remained at 13.2 +/- 6.2 mmHg. Although it slowly decreased, the pressure difference persisted even with FDSs lasting 20 s. Lack of true equilibrium pressure could possibly be due to a waterfall mechanism. However, waterfalls were identified neither between the left ventricle and large arteries nor at the level of the diaphragm in supine patients. We therefore suggest that static filling pressures/mean circulatory pressures can only be directly assessed if the time after termination of cardiac pumping is adequate, i.e., >20 s. For humans, such times are beyond ethical options. |
2,271 | Triphasic waveforms are superior to biphasic waveforms for transthoracic defibrillation: experimental studies. | Our objective was to evaluate the efficacy of triphasic waveforms for transthoracic defibrillation in a swine model.</AbstractText>Triphasic shocks have been found to cause less post-shock dysfunction than biphasic shocks in chick embryo studies.</AbstractText>After 30 s of electrically induced ventricular fibrillation (VF), each pig in part I (n = 32) received truncated exponential biphasic (7.2/7.2 ms) and triphasic (4.8/4.8/4.8 ms) transthoracic shocks. Each pig in part II (n = 14) received biphasic (5/5 ms) and triphasic shocks (5/5/5 ms). Three selected energy levels (50, 100, and 150 J) were tested for parts I and II. Pigs in part III (n = 13) received biphasic (5/5 ms) and triphasic (5/5/5 ms) shocks at a higher energy (200 and 300 J). Although the individual pulse durations of these shocks were equal, the energy of each pulse varied. Nine pigs in part I also received shocks where each individual pulse contained equal energy but was of a different duration (biphasic 3.3/11.1 ms; triphasic 2.0/3.2/9.2 ms).</AbstractText>Triphasic shocks of equal duration pulses achieved higher success than biphasic shocks at delivered low energies: <40 J: 38 +/- 5% triphasic vs. 19 +/- 4% biphasic (p < 0.01); 40 to <50 J: 66 +/- 7% vs. 42 +/- 7% (p < 0.01); and 50 to <65 J: 78 +/- 4% vs. 54 +/- 5% (p < 0.05). Shocks of equal energy but different duration pulses achieved relatively poor success for both triphasic and biphasic waveforms. Shock-induced ventricular tachycardia (VT) and asystole occurred less often after triphasic shocks.</AbstractText>Triphasic transthoracic shocks composed of equal duration pulses were superior to biphasic shocks for VF termination at low energies and caused less VT and asystole.</AbstractText> |
2,272 | Ventricular repolarization components on the electrocardiogram: cellular basis and clinical significance. | Ventricular repolarization components on the surface electrocardiogram (ECG) include J (Osborn) waves, ST-segments, and T- and U-waves, which dynamically change in morphology under various pathophysiologic conditions and play an important role in the development of ventricular arrhythmias. Our primary objective in this review is to identify the ionic and cellular basis for ventricular repolarization components on the body surface ECG under normal and pathologic conditions, including a discussion of their clinical significance. A specific attempt to combine typical clinical ECG tracings with transmembrane electrical recordings is made to illustrate their logical linkage. A transmural voltage gradient during initial ventricular repolarization, which results from the presence of a prominent transient outward K(+) current (I(to))-mediated action potential (AP) notch in the epicardium, but not endocardium, manifests as a J-wave on the ECG. The J-wave is associated with the early repolarization syndrome and Brugada syndrome. ST-segment elevation, as seen in Brugada syndrome and acute myocardial ischemia, cannot be fully explained by using the classic concept of an "injury current" that flows from injured to uninjured myocardium. Rather, ST-segment elevation may be largely secondary to a loss of the AP dome in the epicardium, but not endocardium. The T-wave is a symbol of transmural dispersion of repolarization. The R-on-T phenomenon (an extrasystole originating on the T-wave of a preceding ventricular beat) is probably due to transmural propagation of phase 2 re-entry or phase 2 early after depolarization that could potentially initiate polymorphic ventricular tachycardia or fibrillation. |
2,273 | Factor V Leiden mutation and its relation to left atrial thrombus in chronic nonrheumatic atrial fibrillation. | The genetic defect of coagulation factor V, known as factor V Leiden, produces a resistance to degradation by activated protein C and increased venous thrombosis. However, the role of factor V Leiden in the formation of left atrial thrombus with nonrheumatic atrial fibrillation has not been studied. We investigated whether factor V Leiden is a risk factor for left atrial thrombus in patients with nonrheumatic atrial fibrillation. We analyzed clinical, echocardiographic, and biochemical data in 105 consecutive patients with nonrheumatic atrial fibrillation. These patients were divided into two groups: group A (n = 37) with left atrial thrombus and group B (n = 68) without left atrial thrombus. The study also included 42 control subjects. Left atrial thrombus was investigated by using both transthoracic echocardiography and transesophageal echocardiography. Blood samples from the patients and controls were analyzed for the factor V Leiden mutation by DNA analysis, using the polymerase chain reaction. There was no significant difference in the prevalence of factor V Leiden between the patients and control subjects. The prevalence of factor V Leiden mutation was 8.1% (3/37) in patients with left atrial thrombus, and 8.8% (6/68) in patients without left atrial thrombus. The prevalence of factor V Leiden was 7.1% (3/42) in control subjects. The prevalance of factor V Leiden was 10% (2/20) in patients with spontaneous echo contrast and 8% (7/85) in patients without spontaneous echo contrast. Multivariate analyses showed that left ventricular ejection fraction was an independent predictor of left atrial thrombus. Factor V Leiden mutation is not a risk factor for left atrial thrombus formation and spontaneous echo contrast in patients with nonrheumatic atrial fibrillation. |
2,274 | Cardiotoxicity of macrolides, ketolides and fluoroquinolones that prolong the QTc interval. | Macrolides, ketolides and fluoroquinolones as well as other classes of antimicrobial agents have been associated with prolongation of cardiac repolarisation. This effect is most notable with erythromycin, clarithromycin, gatifloxacin, moxifloxacin, levofloxacin and telithromycin. All of these agents produce a blockage of the HERG channel dependent potassium current in myocyte membranes resulting in a prolonged QTc interval which may give rise to polymorphic ventricular tachycardia, Torsades de Pointes or ventricular fibrillation. The risk of malignant arrhythmias is increased by concomitant usage with Type Ia or III anti-arrhythmic agents or with other drugs that prolong the QTc interval or have competitive metabolic routes. Electrolyte disturbances or underlying cardiac disease also increase the risk of ventricular arrhythmias. The best clinical outcome indicator is the incidence of the associated arrhythmias. The rough rank order of risk with these agents, albeit with limited and incomplete data, is in decreasing order; erythromycin, clarithromycin, gatifloxacin, levofloxacin and moxifloxacin. Telithromycin outcomes for associated arrhythmia are yet to be determined. The essential point is that the overall risk of ventricular arrhythmias is very small with these agents but can be reduced further by avoiding their usage for patients with other multiple risk factors for Torsades de Pointes. |
2,275 | Off-pump right atrial thrombectomy for heparin-induced thrombocytopenia with thrombosis. | This report describes a 72-year-old woman with atrial fibrillation who presented with lower extremity ischemia secondary to thromboembolism. After lower extremity thrombectomy, the patient developed heparin-induced thrombocytopenia with thrombosis (HITT). Her postoperative course was complicated by recurrent supraventricular and ventricular tachycardia, secondary to a mobile thrombus in the right atrium extending into the right ventricle. Because administration of heparin was contraindicated, the patient underwent off-pump right atrial thrombectomy during a brief period of inflow occlusion. Postoperatively, she was placed on lepirudin. Her platelet count normalized without any further thrombotic episodes, and she was discharged on warfarin. |
2,276 | Beyond Fontan conversion: Surgical therapy of arrhythmias including patients with associated complex congenital heart disease. | Arrhythmia operations may be extended to patients with failed ablation procedures or associated structural defects requiring surgical intervention. The purpose of this study is to review our experience with arrhythmia operations in 29 patients who did not have Fontan conversions after the introduction of catheter ablation.</AbstractText>Between July 1992 and January 2002, 29 patients had operations for refractory atrial (n = 24) or ventricular (n = 5) arrhythmias. Mechanisms of arrhythmia included atrial reentry (n = 11), atrial fibrillation (n = 5), automatic atrial (n = 3), accessory connections (n = 6), atrioventricular nodal reentry (n = 2), and ventricular tachycardia (n = 5). Median age at operation was 12.3 years (range, 6 days to 45 years). Two patients had structurally normal hearts; the remaining 27 patients underwent concomitant repair of structural heart disease, including atrioventricular valve replacement or repair (n = 8), anatomy-specific repair of Ebstein's anomaly (n = 4), tetralogy of Fallot repair or revision (n = 4), atrial septal defect closure (n = 3), ventricular septal defect repair (n = 2), Mustard takedown with arterial switch (n = 2), initial Fontan (n = 2), right ventricle-to-pulmonary artery conduit revision (n = 2), Norwood procedure (n = 1), 1 ventricular repair for Uhl's anomaly (n = 1), Mustard baffle revision (n = 1), pulmonary valve replacement with aneurysm resection (n = 1), and aortic valve replacement with complex repair (n = 1).</AbstractText>No patient developed heart block, and the surgical mortality rate was 7%. One patient died after Mustard takedown and arterial switch operation, and 1 neonate died after repair of severe Ebstein's anomaly. There was one late death after arterial switch conversion at another institution. Recurrent clinical supraventricular tachycardia was present in 2 patients (2 of 27, 7.4%) and 2 patients had new-onset tachycardias with different underlying mechanisms of arrhythmia at late follow-up (median follow-up 47 months).</AbstractText>Successful surgical therapy of arrhythmias can be performed safely at the time of repair of complex congenital heart disease or in patients with failed catheter ablation procedures. Early consideration for single-stage therapy of arrhythmia and structural heart disease is indicated.</AbstractText> |
2,277 | Is the use of cardiopulmonary bypass for multivessel coronary artery bypass surgery an independent predictor of operative mortality in patients with ischemic left ventricular dysfunction? | l Coronary artery bypass grafting for patients with ischemic left ventricular dysfunction (ILVD) remains superior to medical therapy in terms of long-term survival. Recently, off-pump coronary artery bypass surgery has been shown to be very promising in achieving functional improvements with favorable operative mortality in this challenging group of patients. The aim of this study was to assess the risk factors responsible for operative mortality in this group of patients.</AbstractText>The records of 305 consecutive ILVD patients, who underwent primary isolated coronary artery bypass grafting for multivessel disease at The National Heart and Lung Institute, Imperial College, University of London, between January 1999 and January 2002, were reviewed retrospectively. Patients were considered to have ILVD if they had a left ventricular ejection fraction of 0.30 or less on preoperative coronary angiography. One hundred six patients were operated on using the off-pump coronary artery bypass surgery technique, and 199 patients were operated on using the conventional coronary artery bypass grafting technique with cardiopulmonary bypass. RESU;TS: Seven (6.6%) patients died in the off-pump coronary artery bypass surgery group, whereas 28 (14.1%) patients died in the cardiopulmonary bypass group (p = 0.05). Univariate analysis of all the preoperative characteristics was performed to identify the potential predictors of mortality in the whole group of ILVD patients. Potential predictors of mortality included symptom status (stable/unstable), chronic obstructive airway disease, dyspnea grade III and IV on the New York Heart Association classification, intravenous nitrates, preoperative use of intraaortic balloon pump, ventricular tachycardia or ventricular fibrillation, body surface area less than 2, and cardiopulmonary bypass. Only ventricular tachycardia or ventricular fibrillation was proved to act as an independent predictor of operative mortality in this group of ILVD patients, with an odds ratio of 29.6 (95% confidence interval, 8.9 to 98).</AbstractText>This study showed that using cardiopulmonary bypass for multivessel coronary artery bypass grafting in patients with ILVD was not proved to act as an independent predictor of operative mortality.</AbstractText> |
2,278 | Adult presentation of MCAD deficiency revealed by coma and severe arrythmias. | We report the case of a 33-year-old man who presented with headaches and vomiting. Soon after admission he became drowsy and agitated, developed ventricular tachycardia and his neurological state worsened (Glasgow coma score 6). Blood analysis showed respiratory alkalosis, hyperlactacidemia (8 mmol/l), hyperammonemia (390 micro mol/l) and hypoglycaemia (2.4 mmol/l). Subsequently, he developed supraventricular tachycardia, ventricular tachycardia and ultimately ventricular fibrillation resulting in cardiac arrest, which was successfully treated. A CT scan of the head revealed cerebral oedema. Whilst in the intensive care unit, he developed renal failure and rhabdomyolysis. The metabolic abnormalities seen at the time of admission normalised within 48 h with IV glucose infusion. Biological investigations, including urinary organic acids and plasma acylcarnitines, showed results compatible with MCAD deficiency. Mutation analysis revealed the patient was homozygous for the classical mutation A985G. This is one of only a few reports of severe cardiac arrhythmia in an adult due to MCAD deficiency. This condition is probably under-diagnosed in adult patients with acute neurological and/or cardiac presentations. |
2,279 | Tracking cardiac electrical instability by computing interlead heterogeneity of T-wave morphology. | Oscillations in T-wave morphology, particularly T-wave alternans (TWA), have been fundamentally linked to increased susceptibility to ventricular fibrillation (VF). We investigated whether the escalation in complexity of T-wave oscillations before VF is attributable to increased spatial heterogeneity of repolarization. Peak interlead T-wave heterogeneity (TWH) was measured by second central moment analysis of T-wave morphology in epicardial electrograms in dogs during left anterior descending coronary artery occlusion. TWH differentiated cases in which myocardial ischemia provoked VF from those without VF (563 +/- 56 vs. 139 +/- 36 microV, P < 0.01). In the former group, progressive, significant increases in TWH above preocclusion baseline (70 +/- 8 microV) began at 2.25 min after the start of occlusion and were associated successively with TWA (at 155 +/- 19 microV), T-wave multupling (at 386 +/- 100 microV), complex oscillatory T-wave forms (at 560 +/- 76 microV), discordant TWA (at 572 +/- 98 microV), and VF at 4.36 +/- 0.14 min. TWH in precordial ECGs in 12 pigs during angioplasty-balloon-induced myocardial ischemia also discriminated animals that experienced VF (from 90 +/- 14 at baseline to 382 +/- 39 microV, P < 0.05) from those without VF (from 96 +/- 17 at baseline to 199 +/- 61 microV, NS). Ischemia-induced changes in ST segment and T-wave amplitude did not predict VF. Heightened spatial heterogeneity of repolarization, as assessed by second central moment analysis of TWH, underlies TWA and increased risk for ischemia-induced VF. Monitoring spatial TWH from precordial leads could prove useful in stratifying risk for life-threatening arrhythmias. |
2,280 | [Non-pharmacologic treatment of atrial fibrillation]. | The authors provide an update on non-pharmacological treatment of atrial fibrillation (AF). They emphasize that although antiarrhythmic drugs continue to be first-line therapy for the arrhythmia considered to be a cardiovascular epidemic, clinical research to develop non-pharmacological means of treatment has been unprecedentally intensified during the last decade. Electrical cardioversion is the most successful non-pharmacological method to restore sinus rhythm, also the efficacy and safety of AV node ablation for palliative ventricular rate-controll is established. "Hybrid" therapeutic procedures, involving combinations of pharmacological and non-pharmacological interventions have gained widespread use. Curative transcatheter ablation for arrhythmia prevention is to be considered in case of clinical suggestions that AF is initiated by a primary regular arrhythmia that is amenable to routine catheter ablation (secondary AF). Despite encouraging results, at this point in time, curative catheter ablation for primary AF may offer significant improvement or even cure only for a small subset of patients, mostly young individuals with normal heart, and paroxysmal AF with frequent, symptomatic episodes refractory to multiple antiarrhythmic drugs. These interventions are to be performed in the settings of a clinical research project in some institutions. Regarding pacemaker therapy in case of bradycardia indication, physiologic pacing (AAI or DDD) is associated with significantly lower incidence of atrial fibrillation than ventricular pacing. Large-scale randomized controlled trials are needed to assess the clinical value of specially designed implantable devices to prevent atrial fibrillation in patients with no conventional bradycardia indication. Also, technical optimization and proper clinical evaluation is needed for implantable atrioverters and implantable cardioverter defibrillators capable of atrial cardioversion therapy. |
2,281 | Effects of coupled pacing on cardiac performance during acute atrial tachycardia and fibrillation: an old therapy revisited for a new reason. | Atrial tachycardia (AT) and fibrillation (AF) result in rapid ventricular rates that are detrimental to optimal cardiac function. The purpose of this study was to determine whether the application of a coupled pacing (CP) regimen would improve ventricular function by decreasing the ventricular rate of mechanical contractions (VRMCs). We simulated AT by pacing either atrium at a rate that resulted in a rapid but regular ventricular rate in seven anesthetized dogs. AF was induced by increasing the atrial pacing rate until atrial activation did not follow the pacing. After the induction of either AT or AF, we applied CP after each intrinsic ventricular activation. We measured the VRMCs and left ventricular (LV) pressures and volumes via a pressure-conductance catheter. The marked reductions in VRMCs during CP resulted in increases in LV end-diastolic volume. The CP resulted in virtually no mechanical contractions, whereas the strength of contractions from the normal electrical activation increased. The increases in the positive LV rate of pressure development over time and LV ejection fraction during CP were the result of postextrasystolic potentiation. The average stroke work (area of the pressure-volume loops) increased as a result of CP during both AT and AF. Despite the large increases in stroke volume (approximately 2x) during CP, the changes in cardiac output were moderate because the VRMCs markedly decreased (approximately 1/2). We conclude that CP therapy may be a viable therapy for slowing the heart rate and improving cardiac performance in patients with AT and AF. |
2,282 | Synchronization of ventricular fibrillation with real-time feedback pacing: implication to low-energy defibrillation. | Wavefront synchronization is an important aspect preceding the termination of ventricular fibrillation (VF). We evaluated the defibrillation efficacy of a novel multisite pacing algorithm using optical recording-guided synchronized pacing (SyncP) in the excitable gaps. We compared the effects of SyncP with traditional overdrive pacing (ODP) at 90% of the VF cycle length (VFCL) and high-frequency pacing (HFP; 43-215 Hz) on spontaneous VF termination in isolated rabbit hearts. For SyncP, the pacing current was triggered by the activation of a reference site and was delivered when the optical potential of the pacing site was in an excitable gap. We measured VFCL and the spatial dispersion of VFCL (SDCL) from five points (3 points in the paced area and 2 points in the nonpaced area) and the distribution of phase singularities during the prepacing, pacing, and postpacing periods. The results showed that 1) the VF termination rate of SyncP (16.0%, n = 106) was higher than that of ODP (2.1%, n = 48, P < 0.01) or HFP (1.6%, n = 129, P < 0.0001); 2) energy consumption for SyncP (7.6 +/- 9.3 mJ) was significantly lower than that of ODP (14.0 +/- 14.8 mJ, P < 0.0001); and 3) SyncP, but not ODP or HFP, decreased SDCL in the paced area during the pacing (P < 0.01) and postpacing (P < 0.05) periods compared with the prepacing period. We conclude that SyncP is effective in inducing wavefront synchronization and is more effective at facilitating spontaneous VF termination than non-SyncP. |
2,283 | [Consensus document for the management of patients with atrial fibrillation in hospital emergency departments]. | Atrial fibrillation (AF) is the most prevalent arrhythmia in hospital emergency departments and is a serious disease associated with a twofold increase in morbidity and a high mortality rate. However, the management of AF in this scenario is variable and frequently inadequate. This is probably a consequence of the diverse clinical aspects and therapeutic options to consider in the management of patients with AF. Therefore, implementation of specific, coordinated management strategies by the different care providers involved is needed to improve the quality of care and optimize the use of human and material resources. This document presents the guidelines recommended by the Spanish Society of Cardiology (SEC) and the Spanish Society of Emergency Medicine (SEMES) for the management of AF in hospital emergency departments. These guidelines are based on published scientific evidence and are applicable to most emergency departments in Spain. Specific management strategies are proposed for the conversion and maintenance of sinus rhythm, heart rate control during AF, prophylaxis for thrombi and emboli, and hospital admission and discharge protocols. |
2,284 | Calcium and cardiac arrhythmias: DADs, EADs, and alternans. | Rapid progress has been made in understanding the molecular mechanisms by which calcium ions mediate certain cardiac arrhythmias. Principal advances include imaging of cytosolic calcium in isolated cells and in intact tissues, use of fluorescent indicators and monophasic action potentials to record membrane potentials in isolated tissue, and sequencing of the genes that encode critical ion channel proteins. In this review, five types of arrhythmias are discussed where calcium ion currents, or currents controlled by calcium, appear to be responsible for arrythmogenesis. These include: (1) the delayed afterpotential that occurs in conditions of intracellular calcium overload such as digitalis toxicity; (2) the early afterdepolarization that occurs when action potential duration is prolonged; (3) the slowly conducted calcium-dependent action potential (the slow response) in the SA and AV nodes; (4) the phenomenon of calcium transient alternans during ischemia, which is related to action potential duration alternans and t-wave alternans; (5) catecholamine-induced cardiac arrhythmias in families with mutations of the sarcoplasmic reticulum calcium-release channel. For each type of arrhythmia, the clinical implications of emerging knowledge are discussed. An especially important issue is whether ventricular fibrillation during acute coronary artery occlusion is due to calcium transient alternans. Ventricular fibrillation due to acute ischemia is an important subset of the 400,000 sudden cardiac deaths that occur annually in the U.S. Certain drugs, including beta blockers, fish oils, verapamil, and diltiazem, seem to specifically prevent ventricular fibrillation in this setting, and in most cases an effect of the drug on cytosolic calicum appears to be involved. |
2,285 | [Effect of calcium antagonists verapamil and amlodipine on the risk of development of atrial fibrillation after coronary artery bypass grafting]. | To assess effect of calcium antagonists amlodipine and verapamil on the risk of development of atrial fibrillation after coronary artery bypass surgery.</AbstractText>Of 74 patients subjected to mammary artery and venous coronary bypass grafting with the use of cardiopulmonary bypass 19 received amlodipine and 21 - verapamil.</AbstractText>Attacks of atrial fibrillation during 24 hour ECG monitoring were registered in 22.9% of patients mostly on days 2 and 3 after surgery. In verapamil treated patients atrial fibrillation occurred 1.5-2 times more often than in amlodipine treated patients or in patients receiving no calcium antagonists. This could possibly be explained by pronounced slowing of atrio-ventricular conduction by verapamil at the background of postoperative general "irritation" of the atrial myocardium.</AbstractText> |
2,286 | Prognostic significance of morphometric endomyocardial biopsy analysis in patients with idiopathic dilated cardiomyopathy. | To date, considerable controversy exists on the prognostic significance of morphometric endomyocardial biopsy findings in patients with idiopathic dilated cardiomyopathy (IDC).</AbstractText>Quantitative analyses of interstitial structured tissue, myofibril volume fraction, and myocytic fiber diameters of left ventricular endomyocardial biopsy specimens were performed in 124 patients with IDC.</AbstractText>During 51 +/- 22 months follow-up after left ventricular endomyocardial biopsy, major arrhythmic events, defined as sustained ventricular tachycardia (VT), ventricular fibrillation (VF), or sudden cardiac death, were observed in 24 patients (19%). Death from any cause or heart transplant was observed in 39 patients (31%). The amount of interstitial structured tissue, myofibril volume fraction, and myocytic fiber diameters determined from left ventricular endomyocardial biopsy specimens did not differ significantly between patients with and patients without major arrhythmic events or between patients with and patients without transplant-free survival during follow-up.</AbstractText>Quantitative analysis of the amount of interstitial structured tissue, myofibril volume fraction, and myocytic fiber diameters in left ventricular endomyocardial biopsy specimens does not appear to be useful for predicting arrhythmic events and transplant-free survival in IDC.</AbstractText> |
2,287 | Recent advances in the treatment of arrhythmias. | Advances in endocardial mapping techniques and ablation have greatly increased the indications for catheter-ablation of supraventricular arrhythmias. Rate or rhythm control is a valid treatment option for patients with atrial fibrillation; however, all patients with one or more risk factors should be treated with oral anticoagulants. The early success rate and long-term cure of atrial fibrillation by radiofrequency catheter ablation continues to increase. The number of centers offering this treatment option has increased substantially. Implantable defibrillator-cardioverters are the primary treatment modality for patients with ventricular tachycardia and their role in primary prevention is also being defined. Future advances in arrhythmia management will include improvements in catheter design and energy sources for ablation, and greater monitoring capacity of implantable devices. |
2,288 | Diadenosine-5-phosphate exerts A1-receptor-mediated proarrhythmic effects in rabbit atrial myocardium. | (1) Diadenosine polyphosphates have been described to be present in the myocardium and exert purinergic- and nonreceptor-mediated effects. Since the electrophysiological properties of atrial myocardium are effectively regulated by A(1) receptors, we investigated the effect of diadenosine pentaphosphate (Ap(5)A) in rabbit myocardium. (2) Parameters of supraventricular electrophysiology and atrial vulnerability were measured in Langendorff-perfused rabbit hearts. Muscarinic potassium current (I(K(ACh/Ado))) and ATP-sensitive potassium current (I(K(ATP))) were measured by using the whole-cell voltage clamp method. (3) Ap(5)A prolonged the cycle length of spontaneously beating Langendorff perfused hearts from 225+/-14 (control) to 1823+/-400 ms (Ap(5)A 50 micro M; n=6; P<0.05). This effect was paralleled by higher degree of atrio-ventricular block. Atrial effective refractory period (AERP) in control hearts was 84+/-14 ms (n=6). Ap(5)A>/=1 micro M reduced AERP (100 micro M, 58+/-11 ms; n=6). (4) Extrastimuli delivered to hearts perfused with Ap(5)A- or adenosine (>/= micro M)-induced atrial fibrillation, the incidence of which correlated to the concentration added to the perfusate. The selective A(1)-receptor antagonist CPX (20 micro M) inhibited the Ap(5)A- and adenosine-induced decrease of AERP. Atrial fibrillation was no longer observed in the presence of CPX. (5) The described Ap(5)A-induced effects in the multicellular preparation were enhanced by dipyridamole (10 micro M), which is a cellular adenosine uptake inhibitor. Dipyridamole-induced enhancement was inhibited by CPX. (6) Ap(5)A (</=1 mM) did neither induce I(K(Ado)) nor I(K(ATP)). No effect on activated I(K(Ado/ATP)) was observed in myocytes superfused with Ap(5)A. However, effluents from Langendorff hearts perfused with Ap(5)A 100 micro M activated I(K(Ado)) by using A(1) receptors. (7) Ap(5)A did not activate A(1) receptors in rabbit atrial myocytes. The Ap(5)A induced A(1)-receptor-mediated effects on supraventricular electrophysiology and vulnerability suggest that in the multicellular preparation Ap(5)A is hydrolyzed to yield adenosine, which acts via A(1) receptors. An influence on atrial electrophysiology or a facilitation of atrial fibrillation under conditions resulting in increased interstitial Ap(5)A concentrations might be of physiological/pathophysiological relevance. |
2,289 | Heterogeneous regional endocardial repolarization is associated with increased risk for ischemia-dependent ventricular fibrillation after myocardial infarction. | Repolarization Heterogeneity and Sudden Death Risk.</AbstractText>The aim of this study was to investigate whether the characteristics of endocardial ventricular repolarization are associated with differential risk for sudden death. Prolonged surface QT interval is associated with increased arrhythmic risk after myocardial infarction (MI), but the underlying mechanism of QT prolongation and its relation to lethal arrhythmias are unclear.</AbstractText>Ventricular fibrillation (VF) risk was assessed in 12 dogs 1 month after anterior MI during an exercise test coupled with brief circumflex coronary occlusion. Susceptible dogs (n = 5) developed VF during the brief ischemic episode, whereas resistant dogs did not (n = 7). Surface QT interval was measured at rest. Endocardial electroanatomic catheter maps of left ventricular repolarization were obtained in four unique regions identified by echocardiography and compared between groups. Compared to resistant dogs, susceptible dogs were characterized by prolonged surface QT intervals (240 +/- 10 msec vs 222 +/- 7 msec, P = 0.04). In addition, they had lower baroreflex sensitivity (9.7 +/- 1.5 msec/mmHg vs 28 +/- 9.8 msec/mmHg, P < 0.01) and a tachycardic response to acute ischemia suggesting higher propensity for stronger sympathetic reflexes. Surface QT interval prolongation in susceptible dogs was due to a marked heterogeneity of endocardial left ventricular repolarization (239 +/- 42 msec, basal anterior wall vs 197 +/- 35, lateral wall; P < 0.001). Resistant animals had no regional differences in endocardial repolarization.</AbstractText>Sympathetic activation following MI not only produces adverse structural remodeling but also contributes to adverse electrophysiologic remodeling resulting in heterogeneous ventricular repolarization and in a myocardial substrate conducive to lethal reentrant arrhythmias.</AbstractText> |
2,290 | Fiber orientation and cell-cell coupling influence ventricular fibrillation dynamics. | Cell Coupling Influences VF Dynamics.</AbstractText>The structure of ventricular fibrillation (VF) is influenced by regional differences in action potential durations and perhaps restitution kinetics and fiber anisotropy. The spatial organization of VF was investigated by measuring the cross-correlation (CC) and mutual information (MI) of membrane potential (Vm) oscillations recorded from multiple sites.</AbstractText>Rabbit hearts (n = 6) were retrogradely perfused and stained with di-4-ANEPPS, and VF was elicited by burst pacing. Vm oscillations were recorded optically from multiple locations on the epicardium using a 16 x 16 photodiode array or a 72 x 78 CCD camera. The spatial organization of VF was investigated by calculating the maximum CC (CCmax) and MI (MImax) that can be obtained between any two sites. CCmax and MImax were extended to all pixels and served as indices of the similarities between Vm transients at a reference pixel and all other pixels on the map. We found that maps of CCmax and MImax did not contain discrete regions with high CC or MI. However, CCmax and MImax decreased monotonically with increasing distance between any arbitrarily chosen reference pixel and all other pixels. In VF, maps of CCmax and MImax revealed elliptical gradients of CC and MI that were closely aligned with fiber orientation, with major axis at 127 degrees +/- 8 degrees on the left ventricles.</AbstractText>CC and MI analysis in fibrillation provides new evidence that anisotropy of fiber orientation and cell-cell coupling have a direct influence on VF dynamics.</AbstractText> |
2,291 | Defibrillation causes immediate cardiac dilation in humans. | Defibrillation Causes Dilation.</AbstractText>Prior studies in isolated heart tissue have shown both excitation and deexcitation to be the primary mechanism of defibrillation. This article presents the first evidence in man of deexcitation immediately following defibrillation by tracking the heart's mechanical response.</AbstractText>The geometric changes of the ventricular chambers were measured before and after defibrillation in seven human subjects receiving an implantable cardioverter defibrillator (ICD). The ICD was used to produce approximately three episodes of ventricular fibrillation and defibrillation in each subject. Twenty-two two-dimensional echocardiographic images of the right ventricle (RV) and 11 images of the left ventricle (LV) were recorded and analyzed at 30 frames per second. Just over 2 seconds of each episode were digitized, beginning half a second before the defibrillation shock. Individual frames were analyzed to yield cross-sectional, ventricular chamber area as a function of time. Immediately following defibrillation, ventricular chambers dilated with significant fractional area increase (RV: 1.58 +/- 0.25, LV: 1.10 +/- 0.06), with peak dilation at 194 +/- 114 msec.</AbstractText>Defibrillation causes a rapid increase in ventricular chamber area due to relaxation of the myocardium, suggesting that defibrillation synchronizes the cardiac cells to the deexcited state in man.</AbstractText> |
2,292 | Modulation of intracellular Ca(2+) concentration by tedisamil, a class III antiarrhythmic agent, in isolated heart preparation. | New class III antiarrhythmic/defibrillating compound tedisamil was shown to facilitate termination of atrial and ventricular fibrillation in experimental as well as clinical conditions. However, class III-related inhibition of K(+) current associated with prolongation of repolarization can not solely explain its defibrillating ability. Following recent findings it was hypothesized that defibrillating effect of tedisamil is likely due to its sympathomimetic feature linked with modulation of intracellular calcium. Results of this study obtained in isolated heart preparation showed that elevated intracellular Ca(2+) free concentration was decreased by administration of tedisamil in concentration that did not induce Q-T interval prolongation. Due to species differences the effective concentration was in rat 10(-7) M, while in guinea pig 10(-5) M. On the contrary, further dramatic increase of elevated Ca(2+) was detected upon administration of tedisamil in concentration that markedly prolonged Q-T interval (10(-5) M in rat). It is concluded that defibrillating ability of tedisamil is most likely associated with attenuation of abnormal and harmful intracellular Ca(2+) elevation (that is highly arrhythmogenic) than with prolongation of APD or Q-T interval. |
2,293 | [Hemodynamic consequences of atrial fibrillation]. | Beside supraventricular extra beats, atrial fibrillation is the most common cardiac arrhythmia. Atrial fibrillation according to Douglas P. Zipes definition is an arrhythmia characterised by complete asynchronous atrial depolarisation, without following hemodynamic effective contraction. Atrial electric activity can be detected during electrocardiography as irregular oscillation of the isoelectric line of low and variable amplitude 350-600/min waves. Atrial fibrillation previously considered as a benign arrhythmia is associated with severe clinical complications as hemodynamic disturbances and closely connected with it cerebral embolization. In the present study we focused on left ventricle function during atrial fibrillation. We evaluate a deterious effect of high, irregular heart rate which stimulates left ventricle systolic dysfunction, so called "tachycardiomyopathy". Deterioration of left ventricle systolic function usually coexists with diastolic impairment, which is difficult to treat even if sinus rhythm is restored. We also analysed the pathophysiologic mechanism of left ventricle impairment during atrial fibrillation at cellular level. In second part of this paper we discussed dependence between size and function of left atrium and its appendage and atrial fibrillation induction. One must take into account of vicious circle mechanism induction during atrial fibrillation, which promotes arrhythmia stabilization, as well as after sinus rhythm restoration--may provoke recurrence of arrhythmia. Intracellular changes followed by electrophysiological alteration are regarded as causes of the mentioned mechanism. Accordingly to the newest studies, gene expression plays a role in arrhythmia induction and stabilization. This means that the problem is very complicated and also gives hope to effective treatment of atrial fibrillation including gene modification. |
2,294 | [Evaluating the first German diagnosis-related groups (G-DRG) in cardiological patients: problems in the correct medical and economic grouping]. | About three years ago, the German Government initiated a complete change in the reimbursement system for costs of the in-hospital treatment of patients. A commission of representatives from every component of the German health system decided to adapt the Australian refined Diagnosis Related Groups (AR-DRG system). The AR-DRG system was selected as it would fit best to the German system and because of its high flexibility and preciseness reflecting severity of diseases and treatments. In October 2002, the first German Diagnosis Related Groups (G-DRGs) were calculated from the data of about 116 hospitals. These data now allow first analyses in how far a correct and precise grouping of patients in specific hospital settings is indeed performed and corresponds to the actual costs. Thus, we thoroughly calculated all costs for material and personnel during the in-hospital stay for each patient discharged during the first 4 months of 2002 from our cardiological department. After performing the grouping procedure for each patient, we analyzed in how far inhomogeneous patient distribution in the DRGs occurred and which impact this had on costs and potential reimbursements. Several different problems were identified which should be outlined in this work regarding three G-DRGs: costs of patients who received an implantable cardioverter defibrillator (F01Z) were markedly influenced by multimorbidity and additional expensive interventions which were not reflected by this G-DRG. Use of numerous catheters and expensive drugs represented a major factor for costs in patients with coronary angioplasty in acute myocardial infarction (F10Z) but seemed to be not sufficiently included in the cost weight. A specific area of patient management in our department is high frequency ablation of tachyarrhythmias which is included in other percutaneous interventions (F19Z). Complex procedures such as ablation of ventricular tachycardia or new innovative procedures as ablation of atrial fibrillation were associated with high costs leading to inadequate reimbursement. Furthermore, problems in the associated codes for diseases and procedures became apparent. Opportunities for future optimization such as specific new DRGs, splitting of DRGs, or the impact of changes in reimbursement for high-outliers were discussed. |
2,295 | Optimal defibrillation response intervals for maximum out-of-hospital cardiac arrest survival rates. | Many centers optimize their emergency medical services (EMS) systems to achieve a target defibrillation response interval of "call received by dispatch" to "arrival at scene by responder with defibrillator" in 8 minutes or less for at least 90% of cardiac arrest cases. The objective of this study was to analyze survival as a function of time to test the evidence for this standard.</AbstractText>This prospective cohort study included all adult, cardiac etiology, out-of-hospital cardiac arrest cases from phases I and II of the Ontario Prehospital Advanced Life Support (OPALS) study. Patients in the 21 Ontario study communities received a basic life support level of care with defibrillation by ambulance and firefighters but no advanced life support. Survival was plotted as a function of the defibrillation response interval. The equation of the curve, generated by means of logistic regression, was used to estimate survival at various defibrillation response interval cutoff points.</AbstractText>From January 1, 1991, to December 31, 1997, there were 392 (4.2%) survivors overall among the 9,273 patients treated. The defibrillation response interval mean was 6.2 minutes, and the 90th percentile was 9.3 minutes. There was a steep decrease in the first 5 minutes of the survival curve, beyond which the slope gradually leveled off. Controlling for known covariates, the decrement in the odds of survival with increasing response interval was 0.77 per minute (95% confidence interval 0.74 to 0.83). The survival function predicts, for successive 90th percentile cutoff points, both survival rates and additional lives saved per year in the OPALS communities compared with the 8-minute standard: 9 minutes (4.6%; -18 lives), 8 minutes (5.9%; 0 lives), 7 minutes (7.5%; 23 lives), 6 minutes (9.5%; 51 lives), and 5 minutes (12.0%; 86 lives).</AbstractText>The 8-minute target established in many communities is not supported by our data as the optimal EMS defibrillation response interval for cardiac arrest. EMS system leaders should consider the effect of decreasing the 90th percentile defibrillation response interval to less than 8 minutes.</AbstractText> |
2,296 | Dynamic nature of electrocardiographic waveform predicts rescue shock outcome in porcine ventricular fibrillation. | Survival decreases with duration of ventricular fibrillation, and it is possible that failed rescue shocks increase myocardial damage. Structure in the ECG signal during ventricular fibrillation can be quantified by using the scaling exponent, a dimensionless measure that correlates with ventricular fibrillation duration. This study examined whether the scaling exponent could predict rescue shock success and whether unsuccessful rescue shocks altered the structure of the ventricular fibrillation waveform and the responsiveness to subsequent rescue shocks.</AbstractText>Ventricular fibrillation was electrically induced in 44 anesthetized swine, which were randomly assigned to receive 70-J biphasic rescue shocks at 2, 4, 6, 8, or 10 minutes. If rescue shocks failed, up to 2 subsequent rescue shocks were performed at 2-minute intervals. The scaling exponent was calculated at 1-second intervals from ECG to quantify the organization of the ventricular fibrillation waveform.</AbstractText>A total of 92 rescue shocks were delivered, of which 23 successfully converted ventricular fibrillation to an organized rhythm (immediate success). After these 23 rescue shocks, 14 swine sustained organized rhythms for more than 30 seconds (sustained success). Lower scaling exponent values were associated with increased probability of successful rescue shocks. Receiver operating characteristic curves had an area under the curve of 0.86 for immediate rescue shock success and 0.93 for sustained rescue shock success. Failed rescue shocks increased the rate of scaling exponent increase over time but did not appear to affect subsequent rescue shock success when the scaling exponent was taken into account.</AbstractText>Highly deterministic ventricular fibrillation, reflected by a low scaling exponent, predicted rescue shock success regardless of antecedent failed rescue shocks. In addition, unsuccessful rescue shocks might decrease post-rescue shock ventricular fibrillation waveform organization.</AbstractText> |
2,297 | Specificity and sensitivity of automated external defibrillator rhythm analysis in infants and children. | The rhythm detection algorithms of automated external defibrillators have been derived from adult rhythms, and their ability to discriminate between shockable and nonshockable rhythms in children is largely unknown. This study evaluates the performance of 1 automated external defibrillator algorithm in infants and children and evaluates algorithm performance with anterior-posterior versus sternal-apex lead placement.</AbstractText>We enrolled pediatric patients in a critical care unit, an electrophysiology laboratory, and a cardiac operating room. A monitor-defibrillator recorded ECGs by means of standard defibrillation-monitor pads. Selected 15-second rhythm samples were played into a LIFEPAK 500 automated external defibrillator, and the automated external defibrillator "shock/no shock" decision was documented. To determine sensitivity and specificity, the automated external defibrillator decision was compared with the "shockable" versus "nonshockable" rhythm classification provided by 3 expert clinicians who were blinded to the automated external defibrillator decision.</AbstractText>We recorded 1,561 rhythm samples from 203 pediatric patients (median age 11 months; range, day of birth to 7 years). The automated external defibrillator recommended a shock for 72 of 73 rhythm samples classified as coarse ventricular fibrillation by expert review (sensitivity 99%; 95% confidence interval [CI] 93% to 100%); and correctly reached a "no shock advised" decision for 1,465 of 1,472 rhythm samples classified as nonshockable by experts (specificity 99.5%). Specificity was 99.1% (95% CI 97.8% to 99.8%) with the sternal-apex lead and 99.4% (95% CI 98.1% to 99.9%) with the anterior-posterior lead.</AbstractText>This automated external defibrillator algorithm has high specificity and sensitivity when used in infants and children with either sternal-apex or anterior-posterior lead placement.</AbstractText> |
2,298 | Anesthetic preconditioning: effects on latency to ischemic injury in isolated hearts. | Anesthetic preconditioning (APC) is protective for several aspects of cardiac function and structure, including left ventricular pressure, coronary flow, and infarction. APC may be protective, however, only if the duration of ischemia is within a certain, as yet undefined range. Brief ischemia causes minimal injury, and APC would be expected to provide little benefit. Conversely, very prolonged ischemia would ultimately cause serious injury with or without APC. Previous investigations used a constant ischemic time as the independent variable to assess ischemia-induced changes in dependent functional and structural variables. The purpose of the study was to define the critical limits of efficacy of APC by varying ischemic time.</AbstractText>Guinea pig hearts (Langendorff preparation; n = 96) underwent pretreatment with sevoflurane (APC) or no treatment (control), before global ischemia and 120 min reperfusion. Ischemia durations were 20, 25, 30, 35, 40, and 45 min.</AbstractText>At 120 min reperfusion, developed (systolic-diastolic) left ventricular pressure was increased by APC compared with control for ischemia durations of 25-40 min. Infarction was decreased by APC for ischemia durations of 25-40 min, but not 20 or 45 min. APC improved coronary flow and vasodilator responses for all ischemia durations longer than 25 min, and decreased ventricular fibrillation on reperfusion for ischemia durations longer than 30 min.</AbstractText>Although APC protects against vascular dysfunction and dysrhythmias after prolonged ischemia, protection against contractile dysfunction and infarction in this model is restricted to a range of ischemia durations of 25-40 min. These results suggest that APC may be effective in a subset of patients who have cardiac ischemia of intermediate duration.</AbstractText> |
2,299 | [Long-term follow-up of enlargement annulus aortic valve replacement in small aortic root]. | To investigate the long-term survival of patients after aortic valve replacement with enlarged annulus.</AbstractText>From July 1988 to December 2001, the annulus was enlarged in 45 patients. The enlargement techniques included Manouguian's (39 patients), Nicks's (5) and konno's (1). Doppler echocardiography was performed in 43 patients one month after operation. Left ventricular outflow gradient was derived from continuous Doppler measurements of flow velocity, and effective orifice area was calculated by the continuity equation.</AbstractText>The operative mortality was 4.4% (2/45) in this group. One patient died of ventricular fibrillation and the other, lower output syndrome. All patients were followed up with a cumulative follow-up period of 6.2 years. Neither valve-related deaths nor valve-related complications occurred. 97.6% survivors (42/43) belonged to NYHA class I-II, and 2.4% (1/43), class III. No significant differences were observed in hemodynamic performance of differently sized prostheses for each valve type.</AbstractText>Patient-prosthesis mismatch with heart valve prostheses as demonstrated by the indexed effective orifice area can be avoided by use of Manouguian's annulus enlarging techniques. The hemodynamic performance of these aortic valve prostheses is satisfactory.</AbstractText> |
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