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4,500 | Cardioprotective effect of resveratrol, a natural antioxidant derived from grapes. | The major objective of the present study was to examine the cardioprotective effect of resveratrol, an antioxidant presents in red wines, in the rat after ischemia and ischemia-reperfusion (I-R).</AbstractText>The left main coronary artery was occluded for 30 or 5 min followed by a 30-min reperfusion in anesthetized rats. Animals were preinfused with and without resveratrol before occlusion and the severity of ischemia- and I-R-induced arrhythmias and mortality were compared.</AbstractText>Resveratrol pretreatment had no effect on ischemia-induced arrhythmias nor on mortality. In contrast, a dramatic protective effects were observed against I-R-induced arrhythmias and mortality. Resveratrol pretreatment both reduced the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF). During the same period, resveratrol pretreatment also increased nitric oxide (NO) and decreased lactate dehydrogenase levels in the carotid blood.</AbstractText>Resveratrol is a potent antiarrhythmic agent with cardioprotective properties in I-R rats. The cardioprotective effects of resveratrol in the I-R rats may be correlated with its antioxidant activity and upregulation of NO production.</AbstractText> |
4,501 | Reduction in defibrillation threshold using an auxiliary shock delivered in the middle cardiac vein. | Defibrillation in the middle cardiac vein (MCV) has been shown to reduce ventricular defibrillation thresholds (DFTs). Low amplitude auxiliary shock (AS) from an electrode sutured to the left ventricle at thoracotomy have also been shown to reduce DFT if delivered immediately prior to a biphasic shock (between the ventricular RV and superior vena caval (SVC) electrodes). This study investigates the impact on DFT of an AS shock from a transvenously placed MCV lead system. A standard defibrillation electrode was positioned in the RV in eight anesthetized pigs (35-43 kg). A 50 x 1.8-mm electrode was inserted in the MCV through an 8 Fr angioplasty guide catheter. A 150-V (leading edge) monophasic AS was delivered (95 microF capacitor) from the MCV-->Can with three different pulse widths (3, 5, 7 ms). A primary biphasic shock (PS) (95 microF capacitor, phase 1: 44% tilt, 1.6-ms extension and phase 2: 2.5-ms fixed duration) was delivered from the RV-->Can +/- AS. The four configurations were randomized and DFTs (PS + AS) assessed using a modified binary search. Ventricular fibrillation (VF) was induced with 60 Hz AC followed 10 seconds later by the test shock. The DFTs were compared using repeated measures analysis of variance (ANOVA). All configurations incorporating AS produced significant (P < 0.05) reduction in the DFT compared to no AS (13.8 +/- 7.4 J). There was no difference in the efficacy of differing pulse widths (P > 0.05); 3 ms (11.0 +/- 5.4 J), 5 ms (11.5 +/- 6.0), and 7 ms (10.6 +/- 5.3 J). In conclusion, delivering an AS from a transvenous lead system deployed in the MCV reduces the DFT by 23% compared to a conventional RV-->Can shock alone. |
4,502 | A prospective randomized-controlled trial of ventricular fibrillation detection time in a DDDR ventricular defibrillator. Ventak AV II DR Study Investigators. | Implantable cardioverter defibrillators (ICDs) with dual chamber and dual chamber rate responsive pacing may offer hemodynamic advantages for some ICD patients. Separate ICDs and DDDR pacemakers can result in device to device interactions, inappropriate shocks, and underdetection of ventricular fibrillation (VF). The objectives of this study were to compare the VF detection times between the Ventak AV II DR and the Ventak AV during high rate DDDR and DDD pacing and to test the safety of dynamic ventricular refractory period shortening. Patients receiving an ICD were randomized in a paired comparison to pacing at 150 beats/min (DDD pacing) or 175 beats/min (DDDR pacing) during ICD threshold testing to create a "worst case scenario" for VF detection. The VF detection rate was set to 180 beats/min, and VF was induced during high rate pacing with alternating current. The device was then allowed to detect and treat VF. The induction was repeated for each patient at each programmed setting so that all patients were tested at both programmed settings. Paired analysis was performed. Patient characteristics were a mean age of 69 +/- 11 years, 78% were men, coronary artery disease was present in 85%, and a mean left ventricular ejection fraction of 0.34 +/- 0.11. Fifty-two episodes of VF were induced in 26 patients. Despite the high pacing rate, all VF episodes were appropriately detected. The mean VF detection time was 2.4 +/- 1.0 seconds during DDD pacing and 2.9 +/- 1.9 seconds during DDDR pacing (P = NS). DDD and DDDR programming resulted in appropriate detection of all episodes of VF with similar detection times despite the "worst case scenario" tested. Delays in detection may be seen with long programmed ventricular refractory periods which shorten the VF sensing window and may be avoided with dynamic ventricular refractory period shortening. |
4,503 | Electrophysiological control of ventricular rate during atrial fibrillation. | Thirteen anesthetized canine subjects (17-29 kg) were used to demonstrate that mild cervical left vagal stimulation could control ventricular rate effectively during atrial fibrillation (AF). Two studies are presented. The first study used six subjects to demonstrate the inverse relationship between (manually applied) left vagal stimulation and ventricular excitation (R wave) rate during AF. As left vagal stimulation frequency was increased, ventricular excitation rate decreased. In these studies, a left vagal stimulus frequency of 0-10 per second reduced the ventricular excitation rate from > 200/min to < 50/min. The decreasing ventricular excitation rate with increasing left vagal stimulation frequency was universal, occurring in all 26 trials with the six subjects. This fundamental principle was used to construct an automatic controller for use in the second study, in which seven subjects were used to demonstrate that ventricular rate can be brought to and maintained within a targeted range with the use of an automatic (closed-loop) controller. A 45-minute record of automatic ventricular rate control is presented. Similar records were obtained in all seven subjects. |
4,504 | No gender differences in pacemaker selection in patients undergoing their first implantation. | Recent studies have indicated that women were less likely to receive sophisticated pacemaker devices than men. These differences could not be fully explained by demographic and clinical variables. The purpose of the present study was to assess whether a gender related difference might exist in pacemaker mode selection in patients undergoing their first implantation in The Netherlands. Records of first implants (n = 39,217) collected from 1988 through 1997 covering 95% of all implantations in The Netherlands. From this population 33,564 (85.6%) patients were included for final analysis. We observed no significant sex differences in pacemaker selection in patients with atrioventricular conduction disorders and bundle branch block. In patients with sick sinus syndrome, only very old women (> or = 85 years) had more atrial systems implanted than men of similar age (6.5% vs 3.5%), whereas men received more double chamber pacemakers (12.3% vs 10.3%) (P = 0.002). However, the relative distribution of physiological versus nonphysiological pacemakers in this subgroup was similar for men and women. In patients with chronic atrial fibrillation/flutter associated with bradycardia, sex differences were only apparent in the age group of 75-85 years; women received more dual chamber pacemakers (8.8% vs 5.3%) whereas men received more single chamber ventricular pacemakers (94.2% vs 89.8%) (P = 0.0011). With increasing age, sex differences in pacemaker selection were absent, but there was a considerable drop in implantation rate of dual chamber systems. Our study showed no major sex differences in the selection of pacemaker devices. Physicians select pacemaker devices by age rather than gender, which might be a rational choice. |
4,505 | [Intima-media complex thickness of common carotid artery as a risk factor for stroke]. | Intima-Media Thickness (IMT) of Common Carotid Artery (CCA) could be seen as the atherosclerotic risk factors' final morphological effect. We investigated the hypothesis that IMT of CCA is significantly different in sex- and age-matched groups of persons with stroke and healthy subjects. 47 patients with first-ever atherothrombotic stroke proven by CT were investigated. Patients with atrial fibrillation, valvular heart disease and left ventricular hyperthrophy were excluded. The IMT of CCA were estimated by High-Resolution B-Mode Ultrasonography. All the patients had bilateral IMT measurement within 20 mm proximal to the carotid bulb on the far wall in the anterioposterior and laterolateral plane. The results were compared with those obtained in 50 healthy sex- and age-matched subjects. We found a strong association between IMT and stroke (p < 0.0001). Mean IMT was 0.96 mm (SD 0.18) in patients and 0.70 mm (SD 0.09) in controls. The presence of atherosclerotic plaques was 0.34 and 0.08 for patients and controls respectively (p = 0.0025). IMT of CCA is strongly positively associated with the risk for stroke. The frequency of atherosclerotic plaques in CCAs is statistically significantly higher in stroke patients than in control group. |
4,506 | Experimental study of intermittent crossclamping with fibrillation and myocardial protection: reduced injury from shorter cumulative ischemia or intrinsic protective effect? | During coronary artery revascularization, some surgeons favor intermittent crossclamping with ventricular fibrillation in preference to cardioplegic ischemic arrest for myocardial protection. It is unclear, however, whether intermittent crossclamping with fibrillation is equally protective or whether ischemic injury is reduced as a consequence of shorter cumulative ischemia.</AbstractText>We used isolated, Langendorff-perfused rat hearts, measured preischemic function (left ventricular developed pressure) with an intraventricular balloon, and then subjected the hearts to either (1) 40 minutes of global ischemia, (2) a 2-minute infusion of cardioplegic solution and 40 minutes of ischemia, (3) multidose (every 10 minutes) infusions of cardioplegic solution during 40 minutes of ischemia, (4) continuous ventricular fibrillation during 40 minutes of ischemia, (5) intermittent (4 x 10 minutes) ischemia with 10 minutes of reperfusion, (6) intermittent (4 x 10 minutes) ischemia preceded by intermittent cardioplegia, (7) intermittent (4 x 10 minutes) ischemia with ventricular fibrillation, (8) continuous (40 minutes) ventricular fibrillation during coronary perfusion, or (9) intermittent (4 x 10 minutes) ventricular fibrillation (with perfusion). All protocols were followed by 60 minutes of reperfusion.</AbstractText>After 60 minutes of reperfusion, the percentage recovery of left ventricular developed pressure for groups 1 through 9 was as follows: 32% +/- 2%, 57% +/- 6%, 82% +/- 3%, 19% +/- 3%, 73% +/- 3%, 70% +/- 3%, 78% +/- 4%, 55% +/- 2%, and 57% +/- 3%, respectively. No significant differences were identified among groups 3, 5, and 7, but the percentage recovery of developed pressure in group 3 was significantly higher than that in group 6; the degree of recovery in groups 3 and 5 to 7 was significantly (P <.05) higher than in groups 1, 2, 4, 8, and 9. Early recovery was significantly (P <.05) more rapid in groups 3 and 5 to 9, reaching a plateau (of 55%-80%) by 10 minutes of reperfusion; in groups 1, 2, and 4, the recovery plateau occurred after 50 minutes. Left ventricular end-diastolic pressure was elevated in groups 1, 2, and 4 but was almost unchanged from baseline in the other groups.</AbstractText>A similar level of myocardial protection was achieved with multidose (intermittent) cardioplegia or intermittent crossclamping (with or without fibrillation), indicating that intrinsic preservation by intermittent crossclamping with fibrillation does not exacerbate ischemic injury.</AbstractText> |
4,507 | Effects of extracts from flowering tops of Crataegus meyeri A. Pojark. on ischaemic arrhythmias in anaesthetized rats. | Different species of Crataegus, commonly called Hawthorn, were reported to possess wide pharmacological effects on the cardiovascular system. In the present study, chloroform, ethylacetate and methanol (70%) extracts of the flowering tops of Crataegus meyeri A. Pojark. were studied. The extracts were tested on the incidence and severity of arrhythmias induced by a period of myocardial ischaemia in open-chest anaesthetized male Wistar rats. Infusion of a hydroalcohol extract (1 mg/kg/min) resulted in a significant decrease in the total number of ventricular ectopic beats (from 1494 +/- 362 in the control to 634 +/- 102), mainly by reduction of beats occurring as ventricular tachycardia. A chloroform extract (1 mg/kg/min) also reduced the total number of ventricular ectopic beats but this reduction was due to the decrease of single extrasystoles. A significant reduction in the time spent for ventricular fibrillation was seen by the hydroalcohol and ethylacetate extracts. There were no significant changes in the heart rate and blood pressure during the extract infusion. However, bolus injection of all the extracts caused a significant reduction in the blood pressure. Thus, the extracts of Crataegus meyeri have a hypotensive and a potential antiarrhythmic action on ischaemic myocardium and may possess active principles. |
4,508 | Tolerability of large-dose intravenous levobupivacaine in sheep. | In preclinical pharmacological studies of levobupivacaine (S-bupivacaine), we determined its tolerability, cardiovascular actions, and pharmacokinetics, and we estimated its margin of safety compared with bupivacaine in conscious sheep. Levobupivacaine HCl. H(2)O was infused IV for 3 min into 10 previously instrumented ewes (approximately 50 kg). On subsequent days, the doses were increased by 50 mg from 200 or 250 mg until fatality occurred. All doses produced convulsions, QRS widening, and cardiac arrhythmias. With incremental doses, 4 of 4 animals survived 200 mg, 7 of 10 survived 250 mg, 3 of 7 survived 300 mg, but 0 of 3 survived 350 mg. Death resulted from sudden onset ventricular fibrillation (n = 3, within 2-3 min), electromechanical dissociation-pump failure (n = 5, within 4-5 min), or ventricular tachycardia-induced cardiac insufficiency (n = 2, >10 min). The estimated fatal dose (mean +/- SD) was 277 +/- 51 mg for levobupivacaine (compared with 156 +/- 31 mg found previously for bupivacaine). Pharmacokinetic analysis indicated initial and total distribution volumes = 4.5 (+/-1.6) and 97 (+/-22) L, total clearance = 1.7 (+/-0.4) L/min, and slow half life = 70 (+/-29) min; these values did not differ from those found previously with smaller doses. Heart and brain tissue levobupivacaine concentrations were approximately 3 times those in arterial blood. The doses of levobupivacaine survived were larger than found previously for bupivacaine, indicating its greater margin of safety.</AbstractText>Levobupivacaine produced fatal cardiac toxicity at doses significantly greater than those found in previous studies with bupivacaine. As the two drugs have similar potency for producing clinical nerve blocks, the data imply that levobupivacaine should provide a safer alternative to bupivacaine in practice.</AbstractText> |
4,509 | Vasopressin improves survival after cardiac arrest in hypovolemic shock. | Survival after hypovolemic shock and cardiac arrest is dismal with current therapies. We evaluated the potential benefits of vasopressin versus large-dose epinephrine in hemorrhagic shock and cardiac arrest on vital organ perfusion, and the likelihood of resuscitation. In 18 pigs, 35% of the estimated blood volume was withdrawn over 15 min and ventricular fibrillation was induced 5 min later. After 4 min of cardiac arrest and 4 min of standard cardiopulmonary resuscitation, a bolus dose of either 200 microg/kg epinephrine (n = 7), 0.8 unit/kg vasopressin (n = 7), or saline placebo (n = 4) was administered in a blinded, randomized manner. Defibrillation was attempted 2.5 min after drug administration, and all animals were subsequently observed for 1 h without further intervention. Spontaneous circulation was restored in 7 of 7 vasopressin animals, in 6 of 7 epinephrine pigs, and in 0 of 4 placebo swine. At 5 and 30 min after return of spontaneous circulation, median (minimum and maximum) renal blood flow after epinephrine was 2 (0-31), and 2 (0-48) mL. 100 g(-1). min(-1), respectively; and after vasopressin 96 (12-161), and 44 (16-105) mL. 100 g(-1). min(-1), respectively (P: <.01 between groups). Epinephrine animals developed a profound metabolic acidosis by 15 min after return of spontaneous circulation (mean arterial pH, 7.11 +/- 0.01), and by 60 min all epinephrine-treated animals had died. The vasopressin pigs had (P: = 0.015) less acidosis (pH = 7.26+/-0. 04) at corresponding time points, and all survived > or =55 min (P: < 0. 01). In conclusion, treatment of hypovolemic cardiac arrest with vasopressin, but not with large-dose epinephrine or saline placebo, resulted in sustained vital organ perfusion, less metabolic acidosis, and prolonged survival. Based on these findings, clinical evaluation of vasopressin during hypovolemic cardiac arrest may be warranted.</AbstractText>The chances of surviving cardiac arrest in hemorrhagic shock are considered dismal without adequate fluid replacement. However, treatment of hypovolemic cardiac arrest with vasopressin, but not with large-dose epinephrine or saline placebo, resulted in sustained vital organ perfusion and prolonged survival in an animal model of suspended infusion therapy.</AbstractText> |
4,510 | T wave alternans can decrease after coronary revascularization. | Clinical observations and animal experiments indicate that T wave alternans (TWA) is associated with an increased propensity for ventricular fibrillation, and thus it may be considered as a noninvasive marker of life-threatening ventricular arrhythmias. There is substantial evidence indicating that TWA is an intrinsic property of ischemic myocardium. This study was performed to determine the role of percutaneous transluminal coronary angioplasty (PTCA)-induced myocardial ischemia in the development of TWA and the effects of revascularization. The authors recorded bipolar X, Y, and Z leads of 111 consecutive patients (mean age: 56 years) undergoing PTCA before, during, and 24 hours after the procedure. T wave alternans signal was calculated in 97 patients (43 left anterior descending, 26 right coronary artery, and 28 circumflex or major obtuse margin branch) by fast Fourier transformation technique after signal processing. Twenty-four hours after the procedure, the mean and peak X, Y, and Z values for TWA had all been significantly reduced from baseline and during balloon inflation (p<0.01). The findings point out that induced ischemia could be a trigger for T wave alternans, and successful revascularization can reduce alternans. |
4,511 | Safety and efficacy of high-dose adenosine-induced asystole during endovascular AAA repair. | To assess the safety and efficacy of high-dose adenosine administration to increase the precision of endovascular abdominal aortic aneurysm (AAA) repair using a balloon deployed stent-graft.</AbstractText>From January 1997 to March 1999, 98 AAA patients (79 men; mean age 71 years, range 62-91) were treated with balloon-expandable stent-grafts under an approved protocol. After placing a temporary transvenous ventricular lead or an external transthoracic pacing electrode, adenosine (24 mg initially) was administered in an escalating dose fashion to induce at least 10 seconds of asystole, during which the proximal stent was expanded.</AbstractText>Adenosine dosages ranged from 24 to 90 mg (median 24 mg). Nine (9.2%) self-limiting cardiac events were observed: 2 (2.0%) episodes of transient myocardial ischemia, 2 (2.0%) cases of atrial fibrillation requiring cardioversion, 1 (1.0%) transient left bundle branch block lasting <10 seconds, and 4 (4.1%) prolonged periods of asystole requiring temporary pacemaker activation. There were no cases of bronchospasm or worsening obstructive pulmonary disease, and no patients required inotropic support after adenosine-induced asystole.</AbstractText>Cardiac events following adenosine-induced asystole are infrequent, mild, and easily treated. The perioperative use of high-dose adenosine to ensure precise stent-graft placement appears to be a safe method of inducing temporary asystole during endovascular aortic repair.</AbstractText> |
4,512 | Apical hypertrophic cardiomyopathy due to a de novo mutation Arg719Trp of the beta-myosin heavy chain gene and cardiac arrest in childhood. A case report and family study. | Hypertrophic cardiomyopathy (HCM) is a myocardial disease with variable phenotpye and genotype. To demonstrate that the mutation Arg719Trp in the cardiac beta-myosin heavy chain (beta MHC) gene is a high risk factor for sudden death and can be associated with an unusual apical non-obstructive HCM, we report the case of a 6 1/2 year old boy, who suffered cardiac arrest. The proband had a de novo mutation of the beta MHC gene (Arg719Trp) on the paternal beta MHC allele and a second maternally transmitted mutation (Met349Thr), as was shown previously (Jeschke et al. 1998 (11)). Here we report the clinical phenotype of the proband and of his relatives in detail. The proband had a marked apical and midventricular hypertrophy of the left and right ventricle without obstruction. There was an abnormal relaxation of both ventricles. Holter monitoring detected no arrhythmia. Ventricular fibrillation was inducible only by aggressive programmed stimulation. The boy died 3 1/2 years later after another cardiac arrest due to arrhythmia. Five carriers of the Met349Thr mutation in the family were asymptomatic and had no echocardiographic changes in the heart, suggesting a neutral inherited polymorphism or a recessive mutation. It is concluded that there is an association of the mutation Arg719Trp in the beta-myosin heavy chain with sudden cardiac death in a young child. Disease history in conjunction with the genetic analysis suggests that the implantation of a defibrillator converter would have been a beneficial and probably life saving measure. |
4,513 | [Complications of transesophageal echocardiography with dobutamine]. | The transesophageal echocardiographic approach improves the diagnostic power of transthoracic stress echocardiography. However, it is a seminvasive test and its safety is not well established. Our objective was to compare the incidence of complications of transesophageal and transthoracic dobutamine echocardiography. We collected data from 63 patients with inadequate transthoracic window, who underwent transesophageal dobutamine echocardiography and were compared with 100 patients in whom the transthoracic approach was diagnostic. Baseline blood pressure and heart rate were higher in the first group. There were no differences in those parameters at the end of the test. Neither were atropine administration and side effects more frequent in any of the groups. There were no cases of ventricular fibrillation, ventricular tachycardia, acute myocardial infarction, intractable angina or intolerance to the probe. Side effects were equally present in both groups. Transesophageal dobutamine stress echocardiography is a safe test that can be used in patients with coronary artery disease and poor transthoracic window. |
4,514 | Prognostic implications of ventricular fibrillation in acute myocardial infarction: new strategies required for further mortality reduction. | To determine the changing risk of ventricular fibrillation, the prognostic implications, and the potential long term prognostic benefit of earlier hospital admission, after acute myocardial infarction.</AbstractText>Prospective observational study.</AbstractText>A district general hospital in east London.</AbstractText>1225 consecutive patients admitted to a coronary care unit with acute myocardial infarction.</AbstractText>Time of onset of pain and ventricular fibrillation, and long term survival of patients admitted with acute myocardial infarction.</AbstractText>The rate of ventricular fibrillation in these hospital inpatients was high in the first hour from onset of pain (118 events/1000 persons/h; 95% confidence interval (CI) 50.7 to 231) and fell rapidly to an almost constant low level by six hours; 27.4% of patients with early ventricular fibrillation died in hospital, compared with 11.6% of those without (p < 0.0001), but mortality in patients who survived to hospital discharge was not altered by early ventricular fibrillation (five year survival: 75.0% (95% CI 60.0% to 84.8%) with ventricular fibrillation v 73.3% (95% CI 69.6% to 76.6%) without ventricular fibrillation).</AbstractText>Patients successfully resuscitated from early ventricular fibrillation have the same prognosis as those without ventricular fibrillation after acute myocardial infarction. Faster access to facilities for resuscitation must be achieved if major improvements in the persistently high case fatality of patients after acute myocardial infarction are to be made.</AbstractText> |
4,515 | Hemodynamic collapse, geometry, and the rapidly paced upper limit of ventricular vulnerability to fibrillation by T-wave stimulation. | There is an upper limit to the vulnerability (ULV) of the ventricles to fibrillation (VF) induced by T-wave stimuli. Across species, disease states, and pharmacological treatments, the ULV is correlated to the defibrillation threshold (DF50). However, one factor known to increase the ULV far above the DF50 is rapid pacing. In this article we test the hypothesis that this increase is owing to an accompanying hemodynamic collapse or geometric change. In 18 dogs, T-wave stimuli were delivered from transvenous defibrillating electrodes. The T-wave shock strength that induced VF 50% of the time (the ULV50) was measured using a 10-step Bayesian up-down protocol. T-wave stimuli were delivered after 15 paced beats at one of several rates: normal (80% of the R-R interval), rapid (the interval just fast enough to cause hemodynamic collapse), or 10 milliseconds greater than rapid (which did not cause hypotension). We measured the geometry of the left ventricle at the moment of T-wave stimulation using linear ultrasound. Rapid pacing significantly increased the ULV50 above the normal rate ULV (507 +/- 62.9 vs 379 +/- 70.6 V, P < .005, n = 18), even in the subset without hemodynamic collapse (505 +/- 84.4 vs 394 +/- 66.5 V, P < .005, n = 6). No significant geometric changes were noted between rapid (19.8 mm) and normal (20.6 mm, n = 6, P < NS) pacing, but QT interval reduction appears to correlate with the ULV50 (QT vs ULV50, r > 0, P < .01). Rapid pacing can dramatically increase the measured ULV50. The most likely cause is a concurrent change in the electrophysiology, eg, QT or APD, of the myocardium. As the only known factor to consistently alter the relationship between ULV and the DF50, rapid pacing offers a unique opportunity for the study of the link between defibrillation and ULV testing. |
4,516 | Ventricular arrhythmias. Preventing sudden death with drugs and ICD devices. | Sudden cardiac death occurs most frequently in persons age 50 to 60, and serious ventricular arrhythmias are the cause of death in most cases. The underlying substrate is usually CAD, either a healed infarction or an acute ischemic event. Early studies using antiarrhythmic drugs to improve post-MI survival led instead to increased mortality, casting doubt on this approach. A cascade of studies using newer antiarrhythmic drugs showed some promise in selected patients post MI. Another approach--using implantable defibrillators--may show greater benefit than antiarrhythmic drugs in patients at serious risk, but the widespread implantation of these devices may be cost-prohibitive. Management of serious ventricular arrhythmias is guided by the individual patient's comorbidities, cardiac function, history of ischemia, and perceived risk of sudden death. |
4,517 | Emerging indications for permanent pacing. | New indications for pacing are being investigated in the areas of vasovagal syncope, hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, and atrial fibrillation. It is hoped that pacing will offer an alternative therapy to patients who are refractory to medical therapy. Although pacing for vasovagal syncope continues to be controversial, it appears that a highly symptomatic group with a predominately cardioinhibitory component can benefit. Current data indicate that dual-chamber pacing should not be considered therapeutically equal to septal myectomy in patients with hypertrophic obstructive cardiomyopathy, but may be considered in those more than 65 years of age, or in others who are not good surgical candidates. Biventricular or left ventricular pacing appears promising in heart failure patients and may be combined with implantable cardioverter-defibrillator therapy. Lead technology for coronary vein placement needs further improvement. Dual-site atrial pacing appears to help prevent recurrences of atrial fibrillation and may become a useful adjunct to drug, ablative, and implantable cardioverter-defibrillator therapies. |
4,518 | Implantable dual-chamber cardioverter-defibrillator-pacemaker. | The fifth generation of implantable cardioverter-defibrillators offer enhanced modes of detection of atrial and ventricular arrhythmias, antitachycardia pacing and shocks, multiprogrammability, intracardiac electrogram storage, and all functions of antibradycardia dual-chamber pacing including rate responsiveness and mode switching. There is no consensus on the indications for dual-chamber pacemaker defibrillator systems. This review focuses on the four major options of newer devices that might benefit patients: 1) permanent dual-chamber pacing in ischemic coronary disease patients, 2) detection and management of atrial fibrillation or other atrial tachyarrhythmias, 3) some newer indications for pacing, and 4) the suppression of inappropriate interventions. On the basis of published data, newer indications for the dual-chamber systems, advantages and limitations, and future perspectives are discussed. |
4,519 | Epidemiology of hypertrophic cardiomyopathy-related death: revisited in a large non-referral-based patient population. | Death resulting from hypertrophic cardiomyopathy (HCM), particularly when sudden, has been reported to be largely confined to young persons. These data emanated from tertiary HCM centers with highly selected referral patterns skewed toward high-risk patients.</AbstractText>The present analysis was undertaken in an international population of 744 consecutively enrolled and largely unselected patients more representative of the overall HCM spectrum. HCM-related death occurred in 86 patients (12%) over 8+/-7 years (mean+/-SD). Three distinctive modes of death were as follows: (1) sudden and unexpected (51%; age, 45+/-20 years); (2) progressive heart failure (36%; age, 56+/-19 years); and (3) HCM-related stroke associated with atrial fibrillation (13%; age, 73+/-14 years). Sudden death was most common in young patients, whereas heart failure- and stroke-related deaths occurred more frequently in midlife and beyond. However, neither sudden nor heart failure-related death showed a statistically significant, disproportionate age distribution (P=0.06 and 0.5, respectively). Stroke-related deaths did occur disproportionately in older patients (P=0.002). Of the 45 patients who died suddenly, most (71%) had no or mild symptoms, and 7 (16%) participated in moderate to severe physical activities at the time of death.</AbstractText>HCM-related cardiovascular death occurred suddenly, or as a result of heart failure or stroke, largely during different phases of life in a prospectively assembled, regionally based, and predominantly unselected patient cohort. Although most sudden deaths occurred in adolescents and young adults, such catastrophes were not confined to patients of these ages and extended to later phases of life. This revised clinical profile suggests that generally held epidemiological tenants for HCM have been influenced considerably by skewed reporting from highly selected populations. These data are likely to importantly affect risk stratification and treatment strategies importantly for the prevention of sudden death in HCM.</AbstractText> |
4,520 | Infarct size and recurrence of ventricular arrhythmias after defibrillator implantation. | Infarct size as determined by perfusion imaging is an independent predictor of mortality after implantable cardioverter defibrillator (ICD) implantation in patients with coronary artery disease (CAD) and life-threatening ventricular arrhythmias (VA). However, its value as a predictor of VA recurrence and hospitalisation after ICD implantation is unknown. Therefore, the objective of this study was to evaluate whether infarct size as determined by perfusion imaging can help to identify patients who are at high risk for recurrence of VA and hospitalisation after ICD implantation. We studied 56 patients with CAD and life-threatening VA. Before ICD implantation, all patients underwent a uniform study protocol including a thallium-201 stress-redistribution perfusion study. A defect score as a measurement of infarct size was calculated using a 17-segment 5-point scoring system. Study endpoints during follow-up were documented episodes of appropriate anti-tachycardia pacing and/or shocks for VA and cardiac hospitalisation for electrical storm (defined as three or more appropriate ICD interventions within 24 h), heart failure or angina. After a mean follow-up of 470+/-308 days, 22 patients (39%) had recurrences of VA. In univariate analysis, predictors for recurrence were: (a) ventricular tachycardia (VT) as the initial presenting arrhythmia (86% vs 59% for patients without ICD therapy, P=0.04), (b) treatment with beta-blockers (36% vs 68%, P=0.03) and (c) a defect score (DS) > or = 20 (64% vs 32%, P=0.03). In multivariate analysis, VT as the presenting arrhythmia (chi2=5.51, P=0.02) and a DS > or = 20 (chi2=4.22, P=0.04) remained independent predictors. Cardiac hospitalisation was more frequent in patients with a DS > or = 20 (44% vs 13% for patients with DS < 20, P=0.015) and this was particularly due to more frequent hospitalisations for electrical storm (24% vs 3% for patients with DS < 20, P=0.037). The extent of scarring determined by perfusion imaging can separate patients with CAD into high- and low-risk groups for recurrence of VA and cardiac hospitalisation after ICD implantation. |
4,521 | Swinging motion of intimal flap through the aortic valve in acute aortic dissection. | The purpose of this article is to present a very rare case of Stanford type A acute aortic dissection featuring a swinging motion of the cylinder-shaped intimal flap through the aortic valve. The patient was a 62-year-old male suffering from severe cardiogenic shock. A transthoracic echocardiogram revealed aortic dissection and severe aortic regurgitation. A transesophageal echocardiogram demonstrated that the aortic dissection in the ascending aorta was circumferential and the proximal portion of the intimal flap was swinging through the aortic valve, ie., falling into the left ventricle during the diastolic phase and being ejected back into the ascending aorta during the systolic phase. An emergency graft replacement of the ascending aorta was performed. During ventricular fibrillation under total cardiopulmonary bypass, we performed cardiac massage to prevent myocardial ischemia, because blood flow from a heart lung machine inverted the intimal flap, which might have disturbed the coronary circulation. The patient's postoperative course was uneventful, and his postoperative echocardiogram revealed only a trace of regurgitant flow through the aortic valve. Back-and-forth movement of the cylinder-shaped intima requires coexistence of the following three conditions: severe aortic regurgitation, circumferential dissection, and complete transection of the intimal flap. We conclude that this movement of the intimal flap should be regarded as one of the most serious complications leading rapidly to cardiogenic shock. From a surgical point of view, it is most important to prevent myocardial ischemia during cardiopulmonary bypass especially in cases in which ventricular fibrillation has occurred. We describe the ways to prevent myocardial ischemia in this rare situation. |
4,522 | 4-aminopyridine inhibits the occurrence of ventricular fibrillation but not ventricular tachycardia in the reperfused, P6olated rat heart. | The 4-aminopyridine (4-AP)-sensitive transient outward current (Ito) has been reported to play an important role in the ischemia- or high [Ca2+]o-induced reentrant ventricular arrhythmias. However, the role of 4-AP sensitive Ito in reperfusion arrhythmia remains unknown. Rat hearts were perfused with Tyrode solution (control), and treated with 0.5 micromol/L verapamil, 1 micromol/L glibenclamide, 10 micromol/L E-4031 or 2 mmol/L 4-AP. After a 10-min perfusion, hearts were subjected to 30-min global ischemia followed by 10-min reperfusion. The effects of the ion-channel blockers on the incidence of ventricular tachycardia (VT), torsades de pointes (Tdp) and ventricular fibrillation (VF) during the reperfusion period were investigated. Verapamil and 4-AP abolished VF and Tdp. The incidence of VT was also attenuated by verapamil, but not by 4-AP. Glibenclamide and E-4031 (a blocker of a rapidly activating component of delayed rectifier K+ current) did not affect the incidence of those tachyarrhythmias. Accordingly, (1) the underlying mechanism of VF or Tdp is different from that of VT, and (2) 4-AP sensitive Ito is required for the occurrence of reperfusion Tdp or VF in the present model. |
4,523 | The Brugada syndrome. Outcome of one case. | The Brugada syndrome is a rare condition, and due to its mutating manner of presentation it may be difficult to diagnose. We report one case and discuss the diagnostic aspects and the clinical outcome of one patient with characteristic findings of this syndrome. These findings are especially defined by J-ST elevation in the right leads of serial electrocardiographic records, wide oscillations of J points and ST segments during 24-hour Holter monitoring, and nocturnal sudden death. We stress the importance of the Holter monitor findings for diagnostic complementation. Through this method it is possible to establish a correlation between vigil activities and sleep and the variability of the degree of impairment in ventricular repolarization. |
4,524 | Anticoagulant use in nonvalvular atrial fibrillation. Determining risk and choosing the safest course. | Previous TIA or stroke, diabetes, advanced age, impaired left ventricular function, and a history of hypertension are strong risk factors in patients with nonvalvular AF. When none of these factors is present, aspirin in a dose of 325 mg offers effective protection against future stroke. When any of these factors are present, warfarin adjusted to an INR of 2.0 to 3.0 offers greater protection against future stroke than aspirin alone or aspirin and fixed-dose warfarin (INR 1.2-1.5). More data are needed before newer anticoagulants can be recommended for treatment. |
4,525 | Radiofrequency catheter ablation for the treatment of supraventricular tachycardias in children and adolescents. | We report our experience in radiofrequency catheter ablation between April, 1992 and December, 1998, in which we treated 287 patients less than 18 years of age (mean 14.3 +/- 3.1 years) with supraventricular tachycardia. Accessory, pathways were the arrhythmic substrate in 252 of the patients (87.8%), the patients having a total of 265 accessory pathways. Atrioventricular nodal re-entry was the cause of tachycardia in 26 patients (9.0%), while atrial flutter was detected in the remaining 9 patients (3.1%). We were able successfully to eliminate the accessory pathway in 236 patients (89%), but 25 patients had recurrent arrhythmias. Ablation proved successful in all cases of atrioventricular node re-entry tachycardia, the slow pathway being ablated in 25 patients, and the fast pathway in only one case. Recurrence of the arrhythmia occurred in three patients (11.5%). We performed a second ablation in these children, all then proving successful. The ablation was successful in all cases of atrial flutter, with one recurrence (11.1%). Overall, therefore, ablation was immediately successful in 271 patients (94.4%), with a recurrence of the arrhythmia in 29 cases (10.7%). The incidence of serious complications was 2.09%. There was one late death due to infective endocarditis, 3 patients suffered complete heart block, 1 had mild mitral regurgitation, and 1 patient developed an haematoma in the groin. We conclude that radiofrequency catheter ablation can now be considered a standard option for the management of paroxysmal supraventricular tachycardias in children and young adults. |
4,526 | Outcomes of out-of-hospital ventricular fibrillation: their association with time to defibrillation and related issues in the defibrillation program in Japan. | The aim of this study was to provide data on the outcomes of out-of-hospital cardiac arrest caused by ventricular fibrillation (VFOHCA) and analyze factors influencing patient outcomes in order to further improve EMS system performance in the resuscitation of VFOHCA patients in Japan. A datasheet was mailed to the fire defense headquarters throughout Japan, and returned data were analyzed for 614 cases of VFOHCA that occurred from January 1 through December 31, 1996. In relation to the time interval from receipt of emergency call to defibrillation, the subjects were stratified into five groups: 0-8 (n = 39), 9-12 (n = 87), 13-16 (n = 154), 17-20 (n = 118) and more than 21 min (n = 216). The discharge survival rates were 18*, 13.8*, 5.2, 4.2 and 4.2%, respectively (*P < 0.05). When defibrillation was delivered within 12 min after a call, 30.2% (38/126) converted to pulse-generating rhythm (PGR) after defibrillation and 43.6% (17/39) of patients with PGR on arrival at the hospital survived to discharge. In spite of these findings, a marked delay to defibrillation (more than 13 min) was observed in the majority (79.5%). The data shown in this study demonstrated that important issues that limit the benefits of an early defibrillation program reside in the EMS system. |
4,527 | Lessons from reporting 100,000 Jamaican electrocardiograms. | The screening programme of the Heart Foundation of Jamaica has found hypertension in 71% of women and 47% of men. Of these patients, 13% were newly discovered hypertensives. Left ventricular hypertrophy was present in 18% of hypertensive women and in 27% of men. Inadequate control of raised blood pressure was a frequent finding. Ischaemic electrocardiographic (ECG) changes were only found in 4% of the 14,739 patients seen in the past two years but this is an underestimation of the prevalence of ischaemic heart disease. Arrhythmias seen over 15 years were usually benign, of sinus origin or ectopics in the absence of heart disease. Uncontrolled atrial fibrillation remains the most serious arrhythmia encountered and usually in hypertensive patients. Obesity found in 80% of women is a problem requiring public education. 'Silent' ischaemia in diabetic and left ventricular hypertrophy in hypertensive patients indicate the need for ECG examination in all newly diagnosed patients with either condition, and annual ECGs thereafter. |
4,528 | Two-year mortality and its determinants following acute myocardial infarction in Trinidad and Tobago. | The purpose of this study was to determine the occurrence of coronary artery disease risk factors in patients presenting with acute myocardial infarction (AMI) to a tertiary care institution in Trinidad and to determine the factors associated with increased mortality following AMI. All patients admitted to the Eric Williams Medical Sciences Complex (EWMSC) between January 1 and December 31, 1996, with a diagnosis of AMI were identified using the hospital admissions and discharge diagnosis databases. Demographic, clinical and laboratory variables were extracted from the hospital case records of patients with confirmed AMI. Sixty-one AMI patients (38 men) were admitted during the study period. Mean age at admission was 60 +/- 11 years with an ethnic case mix of thirty-nine (62%) of East Indian descent, eight (13%) of African descent, twelve (20%) mixed ethnicity and three (5%) of Caucasian descent. Thirty patients (49%) were hypertensive. Thirty-two patients (53%) were diabetic and eighteen patients (30%) gave a history of cigarette smoking. The mean left ventricular ejection fraction was 53 +/- 14%. The mean serum cholesterol from 29 patients was 228.2 +/- 49.0 mg/dl. Increasing age, female gender, an ejection fraction less than 40%, non treatment with streptokinase and in-hospital ventricular fibrillation were associated with poor survival. Multiple regression analyses identified three independent predictors of mortality. These were gender (p = 0.04), in-hospital ventricular fibrillation (p = 0.001) and an ejection fraction less than 40% (p = 0.02). Diabetes mellitus, hypertension, hyperlipidaemia and cigarette smoking were prevalent amongst patients presenting with AMI. Ventricular function was a major determinant of two-year mortality following AMI. Aggressive risk factor modification is recommended to prevent both first and recurrent coronary events. |
4,529 | Management of patients with prosthetic heart valves: potential impact of valve site, clinical characteristics, and comorbidity. | Nearly four decades have passed since the first mechanical prosthetic aortic valve was placed. Since then several design changes and modifications have been made to improve longevity and hemodynamics and reduce thrombogenicity. Despite these advances thromboembolism remains the major problem for mechanical prosthetic valves. The type and the position of the prosthetic valve and several clinical characteristics such as age greater than 70, atrial fibrillation, depressed left ventricular systolic function, left atrial enlargement, left atrial thrombus and a prior history of systemic embolization influence the risk of thromboembolism and the level of anticoagulation needed to prevent this complication. Through clinical experience guidelines have been developed by the American College of Chest Physicians to determine the optimal level of anticoagulation needed to lower the thromboembolic rate with an acceptable hemorrhagic event rate. |
4,530 | A comparison between patients suffering in-hospital and out-of-hospital cardiac arrest in terms of treatment and outcome. | To compare treatment and outcome amongst patients suffering in-hospital and out-of-hospital cardiac arrest in the same community.</AbstractText>All patients suffering in-hospital cardiac arrest in Sahlgrenska University Hospital covering half the catchment area of the community of Göteborg (500 000 inhabitants) and all patients suffering out-of-hospital cardiac arrest in the community of Göteborg. Criteria for inclusion were that resuscitation efforts should have been attempted. TIME OF SURVEY: From 1 November 1994 to 1 November 1997.</AbstractText>Data were recorded both prospectively and retrospectively.</AbstractText>In total, 422 patients suffered in-hospital cardiac arrest and 778 patients suffered out-of-hospital cardiac arrest. Patients with in-hospital cardiac arrest included more women and were more frequently found in ventricular fibrillation. The median interval between collapse and defibrillation was 2 min in in-hospital cardiac arrest compared with 7 min in out-of-hospital cardiac arrest (< 0.001). The proportion of patients being discharged from hospital was 37.5% after in-hospital cardiac arrest, compared with 8.7% after out-of-hospital cardiac arrest (P < 0.001). Corresponding figures for patients found in ventricular fibrillation were 56.9 vs. 19.7% (P < 0.001) and for patients found in asystole 25.2 vs. 1.8% (P < 0.001).</AbstractText>In a survey evaluating patients with in-hospital and out-of-hospital cardiac arrest in whom resuscitation efforts were attempted, we found that the former group had a survival rate more than four times higher than the latter. Possible strong contributing factors to this observation are: (i) shorter time interval to start of treatment, and (ii) a prepared selection for resuscitation efforts.</AbstractText> |
4,531 | Transgenic rat hearts expressing a human cardiac troponin T deletion reveal diastolic dysfunction and ventricular arrhythmias. | Familial hypertrophic cardiomyopathy (FHC) due to mutations of cardiac troponin T (cTnT) is associated with a high frequency of sudden death even in the absence of cardiac hypertrophy. To investigate the causal relationship of cTnT mutations and this particular phenotype, we sought to establish a transgenic rat model for the disease.</AbstractText>Transgenic rats were generated expressing human wild-type cTnT or two truncated cTnT molecules (del ex16, del ex15/16), resulting from an intron 15 splice donor site mutation previously observed in FHC patients. Transgenic rat hearts were characterized by histology, immunohistochemistry and in the 'working heart'.</AbstractText>Human wild-type and del ex16 cTnT were stably expressed and incorporated into the sarcomere of transgenic cardiomyocytes. Del ex16 transgenic rats revealed a lower level of expression (4-5%) than human wt cTnT animals (25-40%). In the 'working heart' model del ex16 hearts exhibited significant systolic and diastolic dysfunction without cardiac hypertrophy. In contrast, human wt cTnT hearts showed improved contractile performance and moderate myocardial hypertrophy. After 6 months of daily physical exercise one del ex16 rat died suddenly and three out of five del ex16 hearts revealed ventricular tachycardia/fibrillation. No arrhythmia was observed in human wt cTnT expressors. Myofibrillar disarray was present in del ex16 hearts after training but not in human wild-type cTnT rats or non-transgenic controls.</AbstractText>A human cTnT deletion overexpressed in transgenic rats exerts a dominant-negative effect and mimics the phenotype of FHC with diastolic dysfunction and arrhythmias. By contrast, human cTnT wild-type animals reveal a gain of function and cardiac hypertrophy without arrhythmias.</AbstractText> |
4,532 | [Sudden cardiac death out of the hospital and early defibrillation]. | Since most sudden cardiac death victims show neither symptoms before the event nor other signs or risk factors that would have identified them as a high risk population before their cardiac arrest, emergency out-of-hospital medical services must be improved in order to obtain a higher survival in these patients. Early defibrillation is an essential part of the chain of survival that also includes the early identification of the victim, activation of the emergency medical system, immediate arrival of trained personnel who can perform basic cardiopulmonary resuscitation and early initiation of advanced cardiac life support that would raise the survival rate for sudden cardiac arrest victims. Many studies have demonstrated the enormous importance of early defibrillation in patients with a cardiac arrest due to ventricular fibrillation. The most important predictor of survival in these individuals is the time that elapses until electric defibrillation, the longer the time to defbrillation the lower the number of patients who are eventually discharged. Multiple studies have demonstrated that automatic external defibrillation will reduce the time elapsed to defibrillation and thus improve survival. For these reason, public access defibrillation to allow the use of automatic external defibrillators by minimally trained members of the lay public, has received increasing interest on the part of a groving number of companies, cities or countries. The automatic external defibrillaton, as performed by a lay person is being investigated. The liberalization of its application, if is demonstrated to be effective, will need to be accompanied by legal measures to endorse it and appropriate health education, probably during secondary education. |
4,533 | Tachycardia-related cardiomyopathy: a common cause of ventricular dysfunction in patients with atrial fibrillation referred for atrioventricular ablation. | To determine the frequency of tachycardia-related cardiomyopathy in patients with atrial fibrillation and systolic dysfunction referred for atrioventricular node ablation.</AbstractText>This prospective multicenter cohort study was conducted at 16 tertiary care centers. The ejection fraction was measured before and 3 and 12 months after atrioventricular node ablation. Patients with reduced systolic function (ejection fraction < or = 45%) before atrioventricular ablation were included in this study. Patients whose ejection fraction increased by at least 15 percentage points and to higher than 45% were considered to have tachycardia-related cardiomyopathy.</AbstractText>Of 63 patients with systolic dysfunction, 48 had at least 1 adequate follow-up echocardiographic study. Sixteen (25%) of the 63 had marked improvement in the ejection fraction (mean +/- SD change, 27 +/- 8 percentage points) to a value higher than 45% after ablation.</AbstractText>Tachycardia-related cardiomyopathy is common in patients with atrial fibrillation and systolic dysfunction referred for atrioventricular node ablation. This diagnosis should be considered in all patients in whom systolic dysfunction occurs subsequent to or concomitant with onset of atrial fibrillation.</AbstractText> |
4,534 | Treating electrical storm : sympathetic blockade versus advanced cardiac life support-guided therapy. | Electrical storm (ES), defined as recurrent multiple ventricular fibrillation (VF) episodes, often occurs in patients with recent myocardial infarction. Because treating ES according to the Advanced Cardiac Life Support (ACLS) guidelines yields a poor outcome, we evaluated the efficacy of sympathetic blockade in treating ES patients and compared their outcome with that of patients treated according to the ACLS guidelines.</AbstractText>Forty-nine patients (36 men, 13 women, mean age 57+/-10 years) who had ES associated with a recent myocardial infarction were separated into 2 groups. Patients in group 1 (n=27) received sympathetic blockade treatment: 6 left stellate ganglionic blockade, 7 esmolol, and 14 propranolol. Patients in group 2 (n=22) received antiarrhythmic medication as recommended by the ACLS guidelines. Patient characteristics were similar in the 2 groups. The 1-week mortality rate was higher in group 2: 18 (82%) of the 22 patients died, all of refractory VF; 6 (22%) of the 27 group 1 patients died, 3 of refractory VF (P<0.0001). Patients who survived the initial ES event did well over the 1-year follow-up period: Overall survival in group 1 was 67%, compared with 5% in group 2 (P<0.0001).</AbstractText>Sympathetic blockade is superior to the antiarrhythmic therapy recommended by the ACLS guidelines in treating ES patients. Our study emphasizes the role of increased sympathetic activity in the genesis of ES. Sympathetic blockade-not class 1 antiarrhythmic drugs-should be the treatment of choice for ES.</AbstractText> |
4,535 | A novel SCN5A mutation associated with idiopathic ventricular fibrillation without typical ECG findings of Brugada syndrome. | Mutations in the human cardiac Na+ channel alpha subunit gene (SCN5A) are responsible for Brugada syndrome, an idiopathic ventricular fibrillation (IVF) subgroup characterized by right bundle branch block and ST elevation on an electrocardiogram (ECG). However, the molecular basis of IVF in subgroups lacking these ECG findings has not been elucidated. We performed genetic screenings of Japanese IVF patients and found a novel SCN5A missense mutation (S1710L) in one symptomatic IVF patient that did not exhibit the typical Brugada ECG. Heterologously expressed S1710L channels showed marked acceleration in the current decay together with a large hyperpolarizing shift of steady-state inactivation and depolarizing shift of activation. These findings suggest that SCN5A is one of the responsible genes for IVF patients who do not show typical ECG manifestations of the Brugada syndrome. |
4,536 | Clinical relevance of silent atrial fibrillation: prevalence, prognosis, quality of life, and management. | Although first described about 100yr ago, atrial fibrillation (AF) is now recognized as the most common of all arrhythmias. It has a substantial morbidity and presents a considerable health care burden. Improved diagnosis and an ageing population with an increased likelihood of underlying cardiac disease results in AF in more than 1% of population. AF is associated with an approximately two-fold increase in mortality, largely due to stroke which occurs at an annual rate of 5-7%. Another risk to survival is heart failure, which is aggravated by poor control of the ventricular rate during AF. Usually AF is associated with a variety of symptoms: palpitations, dyspnea, chest discomfort, fatigue, dizziness, and syncope. Paroxysmal AF is likely to be symptomatic and frequently presents with specific symptoms, while permanent AF is usually associated with less specific symptoms. However, in at least one third of patients, no obvious symptoms or noticeable degradation of quality of life are observed. This asymptomatic, or silent, AF is diagnosed incidentally during routine physical examinations, pre-operative assessments or population surveys. Recently, a very large incidence of generally short paroxysms of AF has been seen in patients with implantable pacemakers or defibrillators and these arrhythmias are often silent. Pharmacological suppression of arrhythmia may be associated with a conversion from a symptomatic to an asymptomatic form of AF. Holter monitoring and transtelephonic monitoring studies have demonstrated that asymptomatic episodes of AF exceed symptomatic paroxysms by twelve-fold or more. Although symptoms may not stem directly from AF, the risk of complications is probably the same for symptomatic and asymptomatic patients. AF is found incidentally in about 25% of admissions for a stroke. Studies in patients with little or no awareness of their arrhythmia condition indicate that unrecognized and untreated AF may cause congestive heart failure. In patients with coronary bypass, AF may not only represent risk for immediate postoperative morbidity and increase hospital resource utilization, but being unrecognized, may produce a significant impact on long-term survival and quality of life. Although silent AF merits consideration for anticoagulation and rate control therapy according to standard criteria, whether antiarrhythmic therapy is relevant in this condition remains unclear. |
4,537 | Cardiovascular effects of intravenous diltiazem in dogs with iatrogenic atrial fibrillation. | Atrial fibrillation (AF) was induced in anesthetized Beagle hounds to determine the dose of diltiazem (D) that resulted in hemodynamic function similar to that observed during sinus rhythm (SR). Dogs were instrumented to record hemodynamic and electrophysiological parameters. Six dogs were given D, IV at cumulative doses of 0.063, 0.188, 0.438, 0.938, and 1.938 mg/kg, whereas 6 other dogs received vehicle in equivalent volumes. Plasma concentrations (PC) of D were measured. A cumulative dose of D between 0.438 and 0.938 mg/kg produced PC of 67.8 to 117.4 ng/mL and resulted in a heart rate (HR) closest to that observed during SR. At doses up to 0.938 mg/kg, no parameter of systolic function fell below that obtained during SR. At a dose of 0.938 mg/kg, the left ventricular end-diastolic and right atrial pressures exceeded those during SR. The rate-pressure product did not differ from that during SR at a dose of 0.938 mg/kg and fell below that during SR at the dose of 1.938 mg/kg. Left ventricular efficiency decreased from SR to AF, returned to values not different from those during SR at a dose of 0.938 mg/kg, and increased to values above those observed during SR at a dose of 1.938 mg/kg. In AF, slowing the HR with 0.438-0.938 mg/kg of D with resultant PC of 67.8-117.4 ng/mL results in cardiovascular function not different from that observed during SR. |
4,538 | Effects of acute gastric distention and recovery on tendency for ventricular arrhythmia in dogs. | The gastric distention-volvulus (GDV) syndrome occurs commonly in large-breed dogs and may prove fatal in 15-68% of cases. Approximately 43% of cases with gastric distention (GD) or volvulus develop cardiac arrhythmias that can contribute to mortality. Most of these arrhythmias are ventricular in origin and ventricular fibrillation (VF) may be the cause of death. This study used an iatrogenic model of acute GD to investigate the prevalence of ventricular arrhythmias during acute GD and its recovery, if programmed electrical stimulation (PES) may uncover tendency to VF, if the Q-T interval corrected for heart rate (Q-Tc) of the electrocardiogram (ECG) predicts tendency to VF, and if hemodynamic changes predate VF. Eleven beagles, anesthetized with morphine and alpha-chloralose, and instrumented so that vascular pressures, cardiac output, and PES could be recorded, were used. Five were unperturbed, whereas acute GD to a pressure of 30 mm Hg for 1.5 hours was produced in 6 others. The results were as follows. No dogs with GD developed spontaneously occurring arrhythmias. VF was produced in no dogs by conventional PES, but occurred in all dogs (P < .05) with GD and none of the controls, using accelerated ventricular pacing. The Q-Tc interval of the ECG prolonged minimally in dogs with GD, and shortened (P < .05) in controls. Some hemodynamic changes did predate VF. In conclusion, dogs with acute GD have a tendency for VF, which may be uncovered by accelerated PES. The mechanism for the vulnerability to arrhythmia with GD is unknown. |
4,539 | Spectral turbulence and late potentials in the signal-averaged electrocardiograms of patients with monomorphic ventricular tachycardia versus resuscitated ventricular fibrillation. | Signal-averaged electrocardiograms (SAECG) were analyzed for late potentials and spectral turbulence in 208 patients with ischemic heart disease with a history of sustained monomorphic ventricular tachycardia (MVT) (n = 62), resuscitation from ventricular fibrillation (VF) (n = 64) or no ventricular tachyarrhythmia (n = 82). Receiver operating characteristic curves were utilized to optimize cut-off values for prediction of MVT and VF. Patients with MVT had a lower ejection fraction (mean = 0.37) than patients with VF (0.44; p = 0.01) and controls (0.48; p < 0.0001). The mean FQRSD in MVT patients (126 ms) was longer than in VF and controls (113 ms; p = 0.005 and 102 ms; p < 0.0001, respectively). The RMS40 was lower in MVT (19 microV) than in VF and controls (29 microV; p = 0.0003 and 28 microV; p < 0.0001, respectively); 81% of the MVT patients were spectral turbulence-positive vs 47% of VF patients and 31% of control patients (p < 0.0001 for both differences). With optimized reference values, FQRSD, TQRSD and ISCSD contributed significantly to the identification of MVT patients and FQRSD to VF patients. The sensitivity of combined time-domain and spectral turbulence analysis was 90% for MVT and 58% for VF, with 63% specificity. MVT patients had a lower ejection fraction and were more often late potential and spectral turbulence positive than VF and control patients. These findings indicate that a large electroanatomic substrate is required in MVT. A long FQRSD was a risk marker for both MVT and VF. Spectral turbulence analysis added independent information, and the combination of time-domain and spectral turbulence analysis was superior to either method alone in identifying the MVT patients. Neither method of analysis, singly nor in combination, performed satisfactorily in identification of VF risk. |
4,540 | [Dilated thyrotoxic cardiomyopathy]. | We report a case of reversible, dilated cardiomyopathy due to thyrotoxicosis, which occurred in a young male without any underlying heart disease. The patient presented a clinical picture of cardiogenic shock related to severe left ventricular dilation and dysfunction and with new-onset atrial fibrillation and very high ventricular rate. In spite of vigorous medical therapy, there was only a mild improvement of clinical and hemodynamic status and ventricular rate persisted inappropriately elevated. Subsequently, laboratory test results allowed for recognition of thyrotoxicosis (secondary to Graves's disease) and then specific thyrostatic treatment was added. There was a prompt clinical improvement and parallel, progressive reversal of left ventricular dysfunction. The patient could be converted to normal sinus rhythm and one week later was discharged in good condition. We discuss the pathophysiological mechanism for the induction of this rare form of thyrotoxic cardiomyopathy and emphasize that awareness of this possible presentation of hyperthyroidism is essential to identify patients with potentially reversible dilated cardiomyopathy. |
4,541 | [Use of percutaneous cardiopulmonary support (PCPS) for extended surgery in patients with T4 tumor]. | Since 1991, we have performed operations for tumors invading the upper airway, left atrium or main pulmonary artery with percutaneous cardiopulmonary support (PCPS) stand by support available. Of 15 cases with PCPS stand by, 6 patients actually underwent operation using PCPS. There were three esophageal cancers invading the carina, two lung neoplasms with left atrial invasion and one neoplasm extending to the main pulmonary artery. One of three patients with esophageal cancer had massive bleeding in the trachea resulting in airway obstruction. For this patient, emergency PCPS was carried out followed by the total removal of the thoracic esophagus and combined resection of membranous portion of the carina. As a result, a substantial amount of time (6 hours) was required. The two patients with reconstruction of the carina due to esophageal cancer were also successfully treated by using PCPS. Two patients with malignant pulmonary neoplasms invading the left atrium underwent combined resection of the lung and left atrium using a combination of PCPS and ventricular fibrillation under normothermia. In conclusion, PCPS should be accepted as a standard technique for patients with advanced thoracic malignancies in whom cardiac arrest or ventilation support is thought to be necessary for the complete removal of the tumor. |
4,542 | Attenuation of KATP channel-opener induced shortening of repolarization time by alpha 1-adrenoceptor antagonist during ischemia in canine heart. | The purpose of the study was to determine whether a new KATP channel opener, Y 26763 (Y), can influence the electrophysiological properties in the ischemic myocardium as well as to determine whether the blunting effect of the alpha 1-adrenoceptor antagonist bunazosin (BN) on an ischemia-induced shortening of repolarization time can be related to the KATP channel activity. The anterior descending branch of the left coronary artery was ligated four times for 5 minutes, separated by 15 minutes of reperfusion (stages 1-4) to test the dose-dependent effect of drugs on repolarization. Dogs received either vehicle (n = 9), Y (0.4, 2.0, and 4.0 micrograms/kg at stages 2, 3, and 4, respectively, with 0.4 microgram/kg/min drip infusion at each of stages 2-4, n = 7), BN (0.1 mg at each of stages 2-4, n = 8), or a combination of these two drugs (BN + Y, the same dose of BN and Y in groups BN and Y, respectively, n = 9). Drugs were administered into the left atrium. The monophasic action potential (MAP) and regional electrograms were recorded. The MAP90 and the duration of the slow deflections (DSD) of the regional electrogram were used as markers of repolarization. The Vmax of the MAP and the rapid deflections (DRD) of the regional electrogram were used as markers of conduction. Y augmented an ischemia-induced shortening of MAP90 and DSD in proportion to an increase in the dose given and the plasma concentration (P < .05-.01), especially at the epicardial site. BN and BN + Y blunted the ischemia-related shortening of MAP90 and DSD, causing a reduction in repolarization time dispersion between the ischemic and normal zones. There were no significant changes in the Vmax or DRD in the ischemic zone between periods before and after an increase in each drug dose in the four groups. None of the seven dogs developed ventricular tachycardia (VT)/ventricular fibrillation (VF) in the Y group, whereas two of the eight dogs in the BN group, three of the nine dogs in the BN + Y group, and three of the nine dogs in the control group developed VT/VF. These results suggest that the alpha 1-adrenergic blocker bunazosin blunts the shortening effect of KATP channel activator on repolarization time, and that the KATP channel opener Y may be antiarrhythmic, although the repolarization time dispersion during myocardial ischemia is increased. |
4,543 | Clusters of ventricular tachycardias signify impaired survival in patients with idiopathic dilated cardiomyopathy and implantable cardioverter defibrillators. | This retrospective study was undertaken to provide data on occurrence, significance and therapy of ventricular tachyarrhythmia (VT) clusters (VTCs) in patients with dilated cardiomyopathy (DCM) and implantable cardioverter defibrillators (ICDs).</AbstractText>Data on the clinical significance of VTCs are lacking in patients with DCM and ICDs.</AbstractText>Baseline characteristics of 106 consecutive patients with DCM and ICDs were prospectively collected, and chart reviews and episode data retrospectively analyzed. A VTC was defined as > or =3 sustained VTs/24 h.</AbstractText>During a mean follow-up of 33+/-23 months, 73 patients (68.9%) had recurrent VT or ventricular fibrillation (VF), 43 patients (40.6%) suffered only single VTs and 30 patients (28.3%) experienced 52 clusters of VTs. Actuarial survival free of VT or VF was 44.6%, 33.0% and 26.5%, and survival free of VTC was 77.3%, 72.2% and 67.1% after one, two and three years, respectively. Independent predictors of VT clusters were heart failure before ICD implantation (p = 0.033), presenting monomorphic VT (p = 0.044), EF <0.40 (p = 0.014) and inducible mVT, especially with right bundle branch block and superior axis configuration (p<0.001). Survival free of recurrent VTCs was 50.8%, 38.1% and 19.0% after one, two and three years, respectively. Once a VTC had occurred, only 56.7%, 46.4%, 30.9% and 15.5% of patients survived and were not transplanted after one, two, three and four years, respectively. Survival was even more reduced if a VTC was associated with cardiac decompensation: 65.6% and 21.9% after one and two years, respectively.</AbstractText>Despite antiarrhythmic intervention, clusters of VTs occur and recur frequently in patients with DCM. They signify impaired survival, especially if they are associated with cardiac decompensation, and may be a harbinger of progressive myocardial deterioration rather than a primarily arrhythmic problem. The benefit of ICD therapy may therefore be low in these patients.</AbstractText> |
4,544 | Ventricular tachycardias above the initially programmed tachycardia detection interval in patients with implantable cardioverter-defibrillators: incidence, prediction and significance. | This retrospective study was performed to provide data on ventricular tachycardias (VT) with a cycle length longer than the initially programmed tachycardia detection interval (TDI) in patients with implantable cardioverter defibrillators (ICDs).</AbstractText>It has been clinical practice to program a safety margin of 30 to 60 ms between the slowest spontaneous or inducible VT and the TDI.</AbstractText>Baseline characteristics of 659 consecutive patients with ICDs were prospectively; follow-up information was retrospectively collected.</AbstractText>During a mean follow-up of 31+/-23 months, 377 patients (57.2%) had at least one recurrent VT or ventricular fibrillation; 47 patients (7.1%) suffered 61 VTs above the TDI. The risk of a VT above the TDI ranged between 2.7% and 3.5% per year during the first four years after ICD implantation. The difference between the cycle length of the slowest VT before ICD implantation, spontaneous or induced, and the first VT above TDI was 108+/-58 ms. Fifty-four VTs (88.5%) above the TDI were associated with significant clinical symptoms (angina or palpitation 63.9%, heart failure 6.6% and syncope 8.2%). Six patients (9.8%) had to be resuscitated. Kaplan-Meyer analysis identified New York Heart Association class II or III (p = 0.021), ejection fraction < 0.40 (p = 0.027), spontaneous (p<0.001) or inducible (p<0.001) monomorphic VTs and the use of class III antiarrhythmic drugs (amiodarone, p<0.001; sotalol, p = 0.004) as risk predictors of VTs above the TDI. The risk of recurrent VTs above TDI was 11.8%, 12.5% and 26.6% during the first, second and third year after first VT above TDI, respectively.</AbstractText>The risk of VTs above the TDI is significantly increased in some patients, and many VTs above TDI cause significant clinical symptoms. A larger safety margin between spontaneous or inducible VTs and the TDI seems to be necessary in selected patients. This is in conflict with an increased risk of inadequate episodes and demands highly specific and sensitive detection algorithms in these patients.</AbstractText> |
4,545 | Intravenous versus oral initial load of propafenone for conversion of recent-onset atrial fibrillation in the emergency room: a randomized trial. | Non-valvular paroxysmal atrial fibrillation is a common clinical condition associated with a high risk of thromboembolism and hemodynamic problems which increase with the duration of arrhythmia. Therefore, even if arrhythmia ceases spontaneously within 24 hours in about half of the patients, a higher early conversion rate is desirable. Propafenone either by intravenous or oral load has been shown effective in conversion to sinus rhythm.</AbstractText>We consecutively randomized all emergency patients with non-valvular atrial fibrillation lasting no more than 48 hours to either intravenous or oral initial load of propafenone. They all received further oral doses if still on atrial fibrillation after the initial load. Exclusion criteria were: mean ventricular rate < 65 b/min, age > 75 years, recent acute myocardial infarction, overt heart failure, conduction defects, ventricular preexcitation, thyroid dysfunction, renal or hepatic insufficiency, pregnancy, current treatment with propafenone or other antiarrhythmic drugs, and intolerance to propafenone. Primary and secondary end-points were the conversion to sinus rhythm within 12 and 48 hours of randomization respectively.</AbstractText>Ninety-seven patients were randomized to intravenous (n = 49) or oral (n = 48) treatment. Overall, sinus rhythm restoration occurred in 83.3% of patients within 12 hours and in 98.9% at 24 hours. Recovery rate resulted significantly greater for intravenous treatment at 1 and 3 hours (p < 0.001 and p = 0.001, respectively). At 6, 12 and 24 hours no significant difference between the two groups was observed (p = 0.77, p = 0.81 and p = 0.99, respectively). No patient needed treatment suspension.</AbstractText>In patients with recent-onset non-valvular atrial fibrillation treated with propafenone within 48 hours, conversion to sinus rhythm occurred in more than 80% within 12 hours. Even if intravenous initial load appears to be slightly more rapid, the oral way is easier to administer and cheaper. The choice may depend on the specific organization of the single emergency room.</AbstractText> |
4,546 | [Pharmacological cardioversion with intravenous propafenone in atrial fibrillation]. | The efficacy and safety of intravenous propafenone for conversion of recent-onset and chronic atrial fibrillation was assessed in 46 patients. 40 with atrial fibrillation associated with or without structural heart disease (mean age 63 +/- 14 years) and 6 patients with atrial fibrillation related to the Wolff-Parkinson-White syndrome (mean age 34.8 +/- 13 years). Propafenone treatment was administered at 2 mg/kg over 15 minutes under continuous electrocardiographic monitoring. In 28 of 32 (87.5%) patients with paroxysmal and/or recent-onset atrial fibrillation a stable sinus rhythm was restored within 1 hour after propafenone (mean 17 +/- 11 minutes) and in only 3 of 8 (37.5%) with chronic atrial fibrillation (p < 0.05). Conversion to sinus rhythm was obtained in 5 of 6 (83.3%) patients with atrial fibrillation related ventricular preexcitation, mean time 21 +/- 12 minutes. Propafenone had an additional effect reducing mean heart rate (141 +/- 21 to 102 +/- 15 beat per minute, p < 0.05) and the shortest preexcited R-R intervals was increased, mean 231.6 +/- 27.8 to 355 +/- 37.2 milliseconds (p < 0.001) in cases associated with ventricular preexcitation. Dizziness, hypotension and transient conduction disturbances occurred in only one patient with rheumatic valvular heart disease: EF 40%. Propafenone is an effective and safe antiarrhythmic drug for converting paroxysmal and/or recent-onset atrial fibrillation of various origins with a more limited efficacy in chronic atrial fibrillation. |
4,547 | Amiodarone-induced bone marrow granulomas. | Amiodarone hydrochloride, a class III antiarrhythmic agent used to treat supraventricular and ventricular cardiac dysrhythmias. In this report we describe two patients receiving amiodarone for atrial fibrillation who underwent bone marrow biopsies to investigate paraproteinaemia (case 1) or severe thrombocytopenia (case 2). Multiple bone marrow granulomas were found in both patients, without evidence of any other cause. In both patients the granulomas disappeared after amiodarone withdrawal, suggesting a direct association. |
4,548 | Early outcome of initiating amiodarone for atrial fibrillation in advanced heart failure. | Little information exists about the early outcomes of initiating amiodarone for atrial fibrillation in patients with advanced heart failure. This study assessed the initial rate of success and complications of amiodarone therapy initiated for patients with atrial fibrillation during hospitalization for heart failure.</AbstractText>We reviewed medical records for 37 consecutive patients with left ventricular ejection fractions </=40% who underwent initiation of amiodarone for atrial fibrillation during hospitalization on a heart failure service.</AbstractText>Atrial fibrillation was present in 35 (95%) and atrial flutter in 2 (5%), with mean duration of 30 months. New York Heart Association class was 3.1 (+/-1.1). Left ventricular ejection fraction was 24% +/- 7%. All patients had received oral amiodarone with an initial dose of 1.2 +/- 0.2 g/day. Bradyarrhythmia led to discontinuation of digoxin in 12 (32%) patients and to permanent pacemaker placement in 7 (19%) patients. Conversion to sinus rhythm occurred spontaneously in 2 patients and after electrical cardioversion in 26 patients, for an initial success of 76%. After a median follow-up of 9.5 months, 21 of 37 (57%) patients remained in sinus or atrial-paced rhythm. Amiodarone complications occurred after discharge in 5 (14%) patients, 4 with hypothyroidism.</AbstractText>Amiodarone with electrical cardioversion has a high initial success rate for treatment of atrial fibrillation in patients with heart failure with advanced systolic dysfunction. The major early side effect was bradyarrhythmia, frequently requiring discontinuation of digoxin or permanent pacemaker placement.</AbstractText> |
4,549 | Percutaneous cardiopulmonary support as a bridge to emergency operation--two surviving cases. | Two patients had percutaneous cardiopulmonary support (PCPS) used as a bridge to emergency surgery. A 66-year-old man admitted with profound cardiogenic shock underwent direct stenting under PCPS with the diagnosis of acute myocardial infarction of the left main trunk, with the intention of performing revascularization as soon as possible. Subsequently, double coronary artery bypass grafting was successfully accomplished. A 69-year-old woman, admitted with acute heart failure due to critical aortic stenosis, manifested cardiogenic shock while undergoing catheterization. PCPS was immediately instituted until the acute deterioration of her hemodynamic state could be reversed, and was continued uneventfully till aortic valve replacement was performed. These results suggest that the current PCPS system is an effective response to acute circulatory collapse and will contributed to the improved survival of patients. |
4,550 | Automatic atrial tachyarrhythmia detection from intracardiac electrograms. | Automatic atrial tachyarrhythmia recognition is crucial in order to allow a correct switching-mode function of dual-chamber pacemakers and to avoid inappropriate shocks of ventricular implantable cardioverter-defibrillators. In this paper we considered three algorithms suitable for implantable devices. The first was based on the atrial cycle length; the others analyze different morphologic characteristics of atrial signals.</AbstractText>Intracardiac bipolar electrogram recordings were obtained from the high right atrium during electrophysiological study. Twenty patients were considered, some of them presenting with different types of cardiac rhythm at different intervals of the study. Cardiac rhythms were divided into three groups: sinus rhythm consisting of 2,196 s obtained from 12 subjects, atrial fibrillation consisting of 771 s obtained from 7 subjects, and atrial flutter consisting of 1,793 s obtained from 7 subjects. The automatic detection was performed on each electrogram segment lasting 1 or 4 s. Atrial segments were separated into two subgroups: the first for the training of the algorithm and the second for testing and validation of results. We considered two types of statistical analysis: comparison between pairs of rhythm (paired classification), and classification among the three different groups (direct classification).</AbstractText>The combination of the cycle length algorithm with a morphological method achieved the best performance for both statistical analyses. Paired classification resulted in the following: atrial fibrillation vs sinus rhythm was detected with no error; atrial flutter vs sinus rhythm with a total accuracy of 99.3% (sensitivity 99.4%, specificity 99.2%); atrial fibrillation vs atrial flutter with a total accuracy of 99.1% (sensitivity 98.5%, specificity 99.4%). The total accuracy achieved for the direct classification was 98.6% (average sensitivity 98.5%, specificity 98.8%).</AbstractText>Our results support the association of algorithms for future enhancement of atrial tachyarrhythmia detection in dual-chamber devices, thanks to the limited computational effort.</AbstractText> |
4,551 | [Administration of adenosine for termination of atrioventricular nodal reentry tachycardia: induction of atrial fibrillation with rapid conduction over an accessory pathway and unmasking of concomitant Wolff-Parkinson-White syndrome]. | The antiarrhythmic properties of adenosine, its ultra-short half-life and the absence of frequent serious side effects make it a front-line agent in arrhythmia management, especially in the treatment of atrioventricular nodal reentrant tachycardia. Due to a shortening of atrial refractoriness, adenosine can facilitate the induction of atrial fibrillation. Life threatening tachycardias may result from a potential rapid conduction of atrial fibrillation over an accessory pathway especially if the latter one has a short antegrade refractory period. We report a case of a 59 year old female patient in which intravenous administration of adenosine during typical atrioventricular nodal reentrant tachycardia was followed by atrial fibrillation with rapid conduction over a hitherto unknown accessory pathway. After intravenous administration of adenosine the tachycardia was terminated successfully within 38 s. After a short period of asystole, spontaneous atrial fibrillation developed unmasking an antegrade preexcitation with subsequent rapid ventricular response (210 b/min). The three-lead ECG showed a narrow QRS complex tachycardia. Because of spontaneous conversion to sinus rhythm and the absence of hemodynamic compromise there was no need for external cardioversion. During electrophysiological study an antidromic atrioventricular reentrant tachycardia was recorded over a left posteroseptal accessory pathway including antegrade conduction properties only. Because of its ultrashort half-life, serious side effects after adenosine administration are rare. The possibility of life threatening proarrhythmias after intravenous adenosine administration should be taken into consideration if the etiology of a paroxysmal supraventricular tachycardia is not clear and a concomitant Wolff-Parkinson-White syndrome cannot be excluded. As with application of all intravenous antiarrhythmic agents, the administration of adenosine should only be performed if continuous ECG monitoring and cardioversion facilities are available and possible. |
4,552 | Control of idiopathic ventricular fibrillation by implantable cardioverter-defibrillator in a child who survived sudden death. | Idiopathic ventricular fibrillation (VF) is extremely rare in children who have not previously undergone cardiac surgery. Patients resuscitated from idiopathic VF remain at risk for recurrence. The use of an implantable cardioverter-defibrillator (ICD) effectively prevents such recurrences. We report the case of a 12-year-old girl who had a history of recurrent syncope and had survived an episode of VF. Serial studies after prolonged but successful resuscitation, including echocardiography, an electrocardiogram (ECG), and coronary angiography failed to reveal abnormal cardiac structures responsible for VF. No abnormal conduction pathways or abnormal early or late after depolarization were found on electrophysiologic study. The ST segments of the 12-lead ECG remained normal after procainamide challenge. The patient underwent ICD implantation 2 weeks after admission and syncope did not recur during a follow-up of 14 months. This report emphasizes that idiopathic VF may be responsible for syncope in children. ICD therapy prevents the recurrence of idiopathic VF and the associated risk of sudden death. |
4,553 | Carotid Doppler high-intensity transient signals in dilated cardiomyopathy. | Thromboembolism is an infrequent but serious complication in dilated cardiomyopathy (DCM), and the role of primary preventive antithrombotic or anticoagulation therapy is undetermined. High-intensity transient signals (HITS) by Doppler ultrasound representing microemboli have been described in various clinical settings associated with increased risk of stroke. This study assessed the feasibility, reproducibility, and prevalence of HITS in patients with DCM.</AbstractText>Thirty patients with severely reduced left ventricular ejection fraction (< or = 35%, mean 25%) and New York Heart Association class II to III who were not receiving antithrombotic or anticoagulant therapy and 20 age-matched normal subjects were prospectively examined. Patients with atrial fibrillation, significant cardiac valvular heart disease, a history of cerebrovascular disease, and those who otherwise required antithrombotic or anticoagulation therapy were excluded. One-hour pulsed-wave Doppler recordings over the common carotid artery (CCA) were performed on 3 separate days in each subject by a single, experienced, blinded sonographer with a 4-MHz probe (TC-2000, Nicolet/EME) with a specially designed probe holder. Studies were read in a blinded, random fashion by 2 independent, experienced HITS Doppler recording readers.</AbstractText>HITS in the CCA were detected in 6 (20%) of 30 patients with DCM and in 3 (15%) of 20 volunteers. This difference was not statistically significant. Intrareader and interreader reproducibility were high (kappa = 0.91 and 0.84, respectively; P <.001), whereas intrasubject reproducibility over the 3 visits was moderate to low (kappa = 0.22). There was no significant difference between HITS characteristics, that is, intensity and duration, in patients versus controls.</AbstractText>The prevalence of CCA HITS in patients with clinically stable heart failure who are not receiving anticoagulation/antithrombotic therapy and are not in atrial fibrillation is low and not significantly different from normal patients. These data suggest that HITS monitoring is not a viable surrogate marker for increased thromboembolic risk in such patients with DCM.</AbstractText> |
4,554 | Influence of coronary anatomy and reimplantation on the long-term outcome of the arterial switch. | Abnormal coronary artery anatomy is reported to have a significant influence on the outcome of the arterial switch operation. This study examines the impact of coronary anatomy and the occurrence of late coronary obstruction on left ventricular (LV) function and long-term outcome.</AbstractText>Coronary artery anatomy, of 170 patients after arterial switch operation (1977-1999), was determined based on operative reports and pre-operative aortograms. Current status was evaluated using ECGs, echocardiograms, scintigraphy, and post-operative coronary angiograms.</AbstractText>In 133/170 patients, coronary artery anatomy consisted of an anterior descending (LAD) and circumflex artery (Cx) from the left sinus and the right coronary artery (RCA) from the right or posterior sinus. The left coronary had an intramural initial course in two of these patients. Fifteen patients had the LAD from the left and Cx and RCA from the right sinus; eight had LAD and RCA from one sinus and Cx from the other; four had single ostium; and three had three separate ostia. Four patients had complex patterns and four patients had a supra commissural coronary. To date, follow-up angiography was performed in 59 patients. Surgical coronary sequellae were found in five patients. Two patients had an occluded left ostium. Initially, they were asymptomatic but showed polymorphic ventricular extrasystoles on ECG and moderate LV dysfunction with large irreversible perfusion defects on scintigraphy. Both patients developed ventricular fibrillation at the age of 14 years. One patient did not survive. The other patient required implantation of a defibrillator. One patient has an occluded RCA, one patient has stenosis of the right ostium and one patient has multiple tortuous collaterals without obstruction of a major branch. In the latter three patients, coronary sequellae were not suspected on ECG, echo, or scintigraphy and were only found on follow-up angiography. Retrograde collateral flow was noted in all three occluded coronaries. LV dysfunction, with normal coronaries, was noted in three patients. All, of these patients, had peri-operative ischaemia suggesting failure of myocardial protection. Two are now asymptomatic with mild LV dysfunction. One patient continues to have severe myocardial dysfunction and secondary aortic insufficiency. A Ross-like procedure was performed placing the original aortic valve in the neo-aortic root. Coronary artery anatomy did not influence early survival or late coronary sequellae.</AbstractText>Abnormal coronary anatomy was not a determinant of outcome in our study. Surgical coronary obstruction is independent of original anatomy. It can be almost silent and is potentially fatal. Follow-up angiography must be considered in all patients after the arterial switch operation.</AbstractText> |
4,555 | Comparison of intravenously administered dofetilide versus amiodarone in the acute termination of atrial fibrillation and flutter. A multicentre, randomized, double-blind, placebo-controlled study. | This study compared the efficacy and safety of intravenous dofetilide with amiodarone and placebo in converting atrial fibrillation or flutter to sinus rhythm.</AbstractText>One hundred and fifty patients with atrial fibrillation or flutter (duration range 2 h-6 months) were given 15-min intravenous infusions of 8 microg. kg(-1)of dofetilide (n=48), 5 mg. kg(-1)of amiodarone (n=50), or placebo (n=52) and monitored continuously for 3 h. Sinus rhythm was restored in 35%, 4%, and 4% of patients, respectively (P<0.001, dofetilide vs placebo;P=ns, amiodarone versus placebo). Dofetilide was more effective in atrial flutter than in atrial fibrillation (cardioversion rates 75% and 22%, respectively;P=0.004). The mean time to conversion with dofetilide was 55+/-15 min. Dofetilide prolonged the QTc interval (+16% at 20 min). Amiodarone substantially decreased the ventricular rate in non-converters (-18 beats. min(-1)at 30 min). Two patients given dofetilide (4%) had non-sustained ventricular tachycardias, and four (8%) had torsade de pointes, in one case requiring electrical cardioversion.</AbstractText>Intravenous dofetilide is significantly more effective than amiodarone or placebo in restoring sinus rhythm in patients with atrial fibrillation or flutter. However, when infused intravenously at this dose and rate, dofetilide causes a significant incidence of torsade de pointes.</AbstractText>Copyright 2000 The European Society of Cardiology.</CopyrightInformation> |
4,556 | Experiences from treatment of out-of-hospital cardiac arrest during 17 years in Göteborg. | To describe changes in different factors at resuscitation and survival in a 17-year survey of patients suffering from out-of-hospital cardiac arrest.</AbstractText>The investigation was carried out in the community of Göteborg with 450 000 inhabitants during 1981-1997 on all patients suffering out-of-hospital cardiac arrest in whom resuscitation was attempted.</AbstractText>The number of cases per year, the proportion of witnessed arrests and the proportion of arrests of cardiac aetiology remained similar over time. There was an increase in median age from 68 to 73 years (P<0.0001), in the proportion of females from 27% to 33% (P=0.035) and in the proportion of patients receiving bystander cardiopulmonary resuscitation from 14% to 28% (P<0.0001) with time. There was a shortening of the median interval from collapse until defibrillation from 9 min to 6 min (P<0.0001) over time but a decrease in the occurrence of ventricular fibrillation as the initially recorded arrhythmia from 39% to 32% (P=0.022). There was an increase in the proportion of patients having a bystander witnessed cardiac arrest of cardiac aetiology being hospitalized alive from 32% to 45% (P<0. 0001 for change over time). The proportion of patients discharged alive from hospital increased from 16% to 29% until 1993, but thereafter decreased to 13% in 1997 (P=0.002 for change over time).</AbstractText>In a survey covering 17 years of resuscitation of out-of-hospital cardiac arrest patients we found that the occurrence of ventricular fibrillation as the initially recorded arrhythmia decreased. There was an increase in age, in the proportion of females and in the use of bystander cardiopulmonary resuscitation. The interval between collapse and defibrillation was shortened. Survival changed over time with an increase until 1993 but with a decrease thereafter.</AbstractText>Copyright 2000 The European Society of Cardiology.</CopyrightInformation> |
4,557 | Prognostic value of the presence and development of atrial fibrillation in patients with advanced chronic heart failure. | To examine whether the presence, or development, of atrial fibrillation in patients with advanced chronic heart failure, is associated with a poorer prognosis, compared to patients with sinus rhythm and chronic heart failure.</AbstractText>We examined 409 patients with moderate to severe chronic heart failure, and compared patients with sinus rhythm (n=325) to those with atrial fibrillation (n=84). At baseline, the two groups were similar regarding most indices of severity of chronic heart failure, such as left ventricular ejection fraction (0.23) and New York Heart Association (NYHA) functional class, while they were different for age (70 years for atrial fibrillation vs 67 years for sinus rhythm patients), aetiology of chronic heart failure, blood pressure, concomitant treatment, and plasma neurohormones (all P<0.05). During a mean follow-up of 3.4 years (range 2.0-5.4), 203 patients (50%) died. The majority of deaths was due to progressive chronic heart failure (55%) or was sudden (28%), but there was no difference in mode of death between sinus rhythm and atrial fibrillation patients. Overall mortality was higher in atrial fibrillation patients (60%), than in those with sinus rhythm (47%; risk ratio 1.40, 95% CI 1.01-1.92, P=0. 04). After adjusting for important prognostic variables, such as age, left ventricular ejection fraction, NYHA class, renal function, and blood pressure, the presence of atrial fibrillation was no longer related to increased mortality (risk ratio 0.86, range 0.59-1.24, P=ns). Of the 325 patients who had sinus rhythm at baseline, 30 (9%) developed atrial fibrillation during the study. These patients were older (70 vs 66 years, P<0.007), and had slightly lower blood pressure and plasma norepinephrine concentrations (P<0.05), but were otherwise similar. During follow-up, mortality was similar in these two groups (47% in those with new onset atrial fibrillation, vs 47% in those who had sinus rhythm throughout the study).</AbstractText>The present data do not support the concept that the presence, or the development of atrial fibrillation in patients with advanced chronic heart failure is independently related to an adverse outcome during long-term follow-up. The generally observed higher mortality in patients with atrial fibrillation thus seems to be related to other factors, associated with atrial fibrillation.</AbstractText>Copyright 2000 The European Society of Cardiology.</CopyrightInformation> |
4,558 | Termination of acute wide QRS complex atrial fibrillation with ibutilide. | Ibutilide is a Vaughan-Williams class III antiarrhythmic agent approved for chemical cardioversion of acute onset atrial fibrillation/flutter. Emergency physicians rarely use ibutilide despite its proven clinical value. We report a case of successful chemical cardioversion using ibutilide in a patient with atrial fibrillation and delayed ventricular depolarization (wide QRS complex). We recommend that ibutilide be considered for wider use in the emergency department and that further studies be conducted. |
4,559 | Changes in chest electrode impedance. | The Prehospital Defibrillation Program in Singapore has in some cases shown a lower amplitude of ventricular fibrillation (VF) than considered the norm. The electrode skin impedance (ESI) refers to the skin impedance determined between two electrodes placed at specific positions on the body surface. The objective of this prospective study was to measure the ESI of patients at 5 Hz and 2 kHz frequencies, and assess its change with time from the application of electrodes, the difference between the ESI at two different sets of electrode placement positions, and correlation with patient factors. Patients who were 25 years or older and not critically ill had their ESI measured with a modified Heart-Save 911 defibrillator, using signal frequencies at 5 Hz and 2 kHz, at 10 seconds, 1 and 2 minutes after electrodes application. Two sets of positions were used; position 1 where an electrode is placed in the right subclavicular region and another just lateral to the apex beat on the left and position 2, which represents the mirror-image of position 1. Thirty-six each of men and women patients were studied. The mean age and weight were 59.9 +/- 13.5 years and 56.8 +/- 24.1 kg respectively. There was no significant correlation between the ESI and patients' body weight or sex. However, there was a significant decrease in the ESI with time from application of electrodes at both positions (P < .05) with the two different frequencies. The ESI was lower when measured at lower frequencies and higher when taken at higher frequencies, but there was no statistically significant difference between the two mirror-image positions used. Thus, with lower frequency, the electrocardiogram amplitude of VF recorded on the automated external defibrillator could be enhanced. |
4,560 | Ventricular arrhythmias. | Sudden cardiac death remains a leading cause of death in the United States. It is usually due to ventricular arrhythmia, either ventricular tachycardia or ventricular fibrillation. The probability of life threatening ventricular arrhythmia correlates closely with underlying structural heart disease. In any patient presenting with a ventricular arrhythmia, a careful search for underlying causes is required, and treatment should be considered primarily if it will prolong survival. Treatment of patients without underlying heart disease who are experiencing ventricular ectopy, and/or nonsustained ventricular tachycardia, consists of reassurance and education. If symptoms are severe, a beta-blocker is an appropriate choice for drug treatment. Patients with ventricular arrhythmia and structural heart disease are generally best managed in conjunction with a cardiologist. |
4,561 | Management of arrythmias. | The management of arrhythmias in elderly patients with congestive heart failure, including atrial fibrillation, ventricular tachyarrhythmias, and bradyarrhythmias, is described. Patients with atrial fibrillation can be treated with rate control anticoagulation for stroke prevention or by attempt at cardioversion and maintenance of sinus rhythm. Elderly patients remaining in atrial fibrillation benefit from anticoagulation provided that no contraindication exists. In patients surviving malignant ventricular arrhythmias, defibrillator implantation is beneficial in elderly patients with heart failure. Prognosis and treatment of nonsustained arrhythmias depends on the presence of underlying cardiac abnormalities. In the healthy elderly population, treatment is not indicated. In patients with coronary artery disease, decreased ejection fraction, and nonsustained ventricular tachycardia, electrophysiology can further stratify risk, and defibrillator implantation can improve survival if arrhythmias are induced. This benefit is as great in elderly patients as in younger patients. Symptomatic bradycardias are increasingly common with advancing age. Symptoms are improved with pacing, with maximum benefit from physiologic rather than ventricular pacing. Although the elderly population poses a unique challenge when faced with arrhythmias, an active approach not only saves lives but also reduces morbidity. |
4,562 | Heart failure complicating acute myocardial infarction. | Older people with congestive heart failure associated with acute myocardial infarction should be treated with loop diuretic therapy. Class I indications for the use of early intravenous beta blockade in patients with acute myocardial infarction are patients without a contraindication to beta blockers who can be treated within 12 hours of onset of myocardial infarction; patients with continuing or recurrent ischemic pain; and patients with tachyarrythmias, such as atrial fibrillation with a rapid ventricular rate. Class I indications for the use of angiotensin-converting enzyme inhibitors during acute myocardial infarction are (1) patients within the first 24 hours of onset of a suspected acute myocardial infarction with ST segment elevation in two or more anterior precordial leads or with clinical heart failure in the absence of significant hypotension or contraindications to the use of angiotensin-converting enzyme inhibitors, (2) patients with myocardial infarction and a left ventricular ejection fraction of less then 40%, (3) and patients with clinical heart failure on the basis of systolic pump dysfunction during and after convalescence from acute myocardial infarction. No class I indications exist for using calcium channel blockers or magnesium during acute myocardial infarction. |
4,563 | Frequency modulation within electrocardiograms during ventricular fibrillation. | Periods of reentrant activation and effective refractory periods are correlated with dominant frequency or reciprocal of cycle periods during ventricular fibrillation (VF). In the present study, we used an analysis technique based on Wigner transforms to quantify time-varying dominant frequencies in electrocardiograms (ECGs) during VF. We estimated dominant frequencies within orthogonal ECGs recorded in 10 dogs during trials of 10 s of VF and in 9 dogs during trials of 30 s of VF. In four additional dogs, we compared dominant frequencies during 10 s of VF before and after administration of amiodarone. Our results showed the following. 1) There was substantial frequency variation or modulation within the ECGs during 10 and 30 s of VF, the average variation being +/-15% from the mean frequency. Amiodarone decreased mean frequencies (P < 0.05) as expected; however, amiodarone also decreased the variation in frequencies (P < 0.05). 2) During 30 s of VF, the dominant frequencies increased continuously from 7.3 to 8.1 Hz (P < 0.05). The increase in frequency was almost linear with a rate of 0.022 Hz/s (r(2) = 0.93, P < 0.0005). 3) Modulation of frequencies during the first and the last one-half of 30 s of VF was not different. Average (in time) mean frequencies and modulation of frequencies were similar in all three ECGs. 4) Although the averages were similar, during any VF episode, dominant frequencies in ECGs recorded from different locations on the body surface were similar to each other at some times and markedly different from each other at other times. We conclude that during VF, 1) frequencies in ECGs vary considerably and continuously, and amiodarone decreases this variation; 2) mean frequencies increase linearly during first 30 s; 3) the variability in frequency does not change during 30 s; and 4) at any given time, the frequencies within spatially different body surface ECGs can be either similar or markedly different. |
4,564 | Mitral annular dynamics during rapid atrial pacing. | Ovine mitral annular area (MAA) reduction predominantly occurs before ventricular systole. We used the myocardial marker methods to investigate left atrial and MAA dynamics during rapid atrial pacing.</AbstractText>Seven sheep underwent implantation of 21 myocardial markers around the mitral annulus, the left ventricle and left atrium. After 7 to 10 days, animals were studied with biplane videofluoroscopy to determine 3-dimensional marker coordinates unpaced and during rapid atrial pacing at 140 minutes(-1). Left ventricle volume, left atrial volume (LAV), and MAA were calculated from marker coordinates. End diastole (ED) was defined at peak of the electrocardiogram R wave; times of minimum MAA and minimum LAV were expressed relative to ED (t = 0). Percent reduction in MAA and LAV were calculated from maximum and minimum values between diastole and early systole.</AbstractText>The time of minimum MAA occurred earlier relative to ED during rapid pacing compared with control (-48 +/- 21 vs 19 +/- 14 msec; P <.001), as did the time of minimum LAV (-47 +/- 18 vs 4 +/- 16 msec; P <.001). Minimum MAA and LAV were significantly smaller with rapid pacing (6. 8 +/- 0.6 vs 6.5 +/- 0.5 cm(2); P <.05, respectively; and 15.4 +/- 2. 4 vs 16.5 +/- 2.3 mL; P <.01, respectively), and a relatively greater fractional reduction in MAA and LAV was observed during presystole.</AbstractText>Rapid atrial pacing resulted in greater MAA and LAV reduction, both of which occurred entirely during diastole. This study supports the notion that MAA reduction is closely linked to LA dynamics.</AbstractText> |
4,565 | Identification of patients at risk by graded exercise testing in an emergency department chest pain center. | The study applied a retrospective follow-up design to determine the prognostic effect of graded exercise testing (GXT) in patients with low- to moderate-risk chest pain evaluated in an emergency department 9-hour protocol chest pain center (CPC) from January 1, 1993 to August 1, 1996. The cohort of 1,209 patients were followed to the date of death or first adverse cardiac event up to 1 year after CPC admission. Cardiac events were defined as coronary artery bypass graft, percutaneous transluminal coronary angioplasty, cardiogenic shock, cardiac-related death, congestive heart failure admission, ventricular tachycardia/ventricular fibrillation arrest, and myocardial infarction. Patients with acute ST-segment elevation or depression of >1 mm, positive enzyme (creatine kinase myocardial band) testing, or unstable angina during their CPC evaluation were admitted without GXT testing. Statistical analysis included chi-square test for complication rates and Cox proportional-hazards modeling. Nine hundred fifty-eight of 1,209 patients underwent GXT testing. Patients with positive, inconclusive, and normal GXTs had complication rates of 36.8% (7 of 19), 3.4% (9 of 267), and 1.1% (5 of 456), respectively. After adjusting for age, sex, and race, the relative risk of complication was 38.9 (95% confidence interval 11.7 to 129.6) with a positive GXT, and 3.6 (95% confidence interval 1.2 to 10.7) with an inconclusive GXT compared with a normal GXT. The GXT is a good prognostic indicator of adverse cardiac events in low- to moderate-risk chest pain in patients evaluated in an emergency department CPC. |
4,566 | Temporal organization of atrial activity and irregular ventricular rhythm during spontaneous atrial fibrillation: an in vivo study in the horse. | Atrial fibrillation (AF) is common in healthy horses. We studied the temporal organization of AF to test the hypothesis that the arrhythmia is governed by a high degree of periodicity and therefore is not random in the horse. Further, we surmised that concealed conduction of AF impulses in the AV node results in an inverse relationship between AF frequency and ventricular frequency.</AbstractText>Fast Fourier transform (FFT) analysis of atrial activity was done on signal-averaged ECGs (n = 11) and atrial electrograms (n = 3) of horses with AF at control (C), after quinidine sulfate (22 mg/kg by mouth every 2 hours) at 50% time to conversion (T50), and immediately before conversion (T90) to sinus rhythm. FFT always revealed a single dominant frequency peak. The mean dominant frequency decreased until conversion (C = 6.84 +/- 0.85 Hz, T50 = 4.87 +/- 1.5 Hz, T90 = 3.41 +/- 1.18 Hz; P < 0.001). Mean AA intervals (n = 500) gradually increased after quinidine. Mean RR intervals (n = 500), standard deviation of the mean (SDM), Poincaré plots, and serial autocorrelograms (SACs) of 500 RR intervals were measured at C and T90 to determine the ventricular response to AF and quinidine-induced changes in the variability of the ventricular response. Mean RR interval and SDM were reduced after quinidine (C = 1431 +/- 266 msec and 695 +/- 23 msec; T90 = 974 +/- 116 msec and 273 +/- 158 msec, respectively; P < 0.01). Poincaré plots and SAC at C and at T90 revealed a significant correlation of consecutive RR intervals typical of a system with a deterministic behavior. At T90, the variability of RR intervals was reduced and the overall periodicity of RR intervals was increased after quinidine administration.</AbstractText>In the horse, AF is a complex arrhythmia characterized by a high degree of underlying periodicity. The inverse AA-to-RR interval relationship and reduced variability of RR intervals after quinidine suggest that the ventricular response during AF results from rate-dependent concealment of AF wavelets bombarding the AV node, which nevertheless results in a significant degree of short-term predictability of beat-to-beat changes in RR intervals.</AbstractText> |
4,567 | Three-dimensional mapping of spontaneous ventricular arrhythmias in a canine thrombotic coronary occlusion model. | Ventricular tachycardia (VT) and ventricular fibrillation (VF) induced by thrombotic coronary occlusion were mapped in three dimensions in ten dogs.</AbstractText>Thrombotic occlusion was induced using a wire to deliver current to the proximal left circumflex artery (LCX). In nine dogs, nonsustained VT (NSVT) arose from numerous focal sites. Sustained VT was initiated in six dogs (VT group) by a focus near or in the ischemic region. VT was maintained by a focus in the ischemic border in three dogs and by macroreentry that involved both the ischemic and nonischemic regions in the other three dogs. In five dogs, VT degenerated into VF due to intramural reentry in different locations. Mean total activation time (AT), the time for activation to traverse the ventricles, for a sinus beat when LCX current was first applied was 40 +/- 4 msec. In the four dogs in which VT occurred 3 to 7 minutes after total occlusion, sinus AT increased to 98 to 146 msec just before VT. Sinus AT in the four dogs without VT was always <98 msec. Mean AT of the first ten cycles of VT was significantly longer in those VTs that degenerated into VF (169 +/- 29 msec) than in those that did not (81 +/- 12 msec).</AbstractText>Thrombotic LCX occlusion induced NSVT in 90%, VT in 60%, and VF in 50% of dogs. Focal mechanisms caused most NSVTs and VT initiation. VT was maintained by a focus near or in the ischemic region or by macroreentry involving both the ischemic and nonischemic regions. AT identified animals in which VT occurred soon after LCX occlusion and in which VT progressed to VF.</AbstractText> |
4,568 | Analysis of the pattern of initiation of sustained ventricular arrhythmias in patients with implantable defibrillators. | The purpose of this study was to analyze the pattern of initiation of sustained ventricular arrhythmias in patients with varying types of underlying structural heart disease.</AbstractText>The study group consisted of 90 patients with an implantable cardioverter defibrillator. Cardiovascular diagnoses included coronary artery disease in 64 patients (71%). The patients were divided into four groups based on the type and severity of structural heart disease. Two hundred sixty episodes of sustained ventricular arrhythmias were analyzed. The mean coupling interval of the initiating beat of all ventricular arrhythmias was 523 +/- 171 msec. The coupling interval of the initiating beat was longer in patients with impaired ventricular function, particularly those with nonischemic dilated cardiomyopathy. The prematurity index was similar regardless of the type of underlying structural heart disease. However, the prematurity index was shorter in patients with polymorphic ventricular tachycardia (VT) compared to those with monomorphic VT. A pause was observed more commonly before the onset of polymorphic VT/ventricular fibrillation than sustained monomorphic VT. Two hundred twenty-two (85%) of the arrhythmia episodes were initiated by a late-coupled premature beat, 33 (13%) were initiated by an early-coupled premature beat, and 5 episodes (2%) were initiated with a short-long-short sequence. The pattern of initiation of the ventricular arrhythmias was similar in all patient groups and for both monomorphic and polymorphic tachycardias.</AbstractText>These findings demonstrate that sustained ventricular arrhythmias typically are initiated by late-coupled ventricular premature depolarizations, regardless of the type or severity of underlying structural heart disease or resultant arrhythmia.</AbstractText> |
4,569 | Intravenous amiodarone for prevention of atrial fibrillation after coronary artery bypass grafting. | Atrial fibrillation occurs in 10% to 40% of patients who undergo coronary artery bypass grafting. This prospective study assesses the safety and efficacy of low-dose intravenous amiodarone in the prevention of atrial fibrillation after coronary artery bypass grafting.</AbstractText>One hundred forty patients were randomly divided into two groups: an amiodarone group (n = 74) receiving intravenous amiadarone in a loading dose of 150 mg and maintenance dose of 0.4 mg x kg(-1) x h(-1) for 3 days before and 5 days after operation and a control group (n = 76) receiving matching infusions of 5% glucose solution.</AbstractText>Atrial fibrillation occurred in 9 (12%) of the amiodarone group patients and in 26 (34%) of the control group patients during hospitalization (p < 0.01). The maximum ventricular rate during atrial fibrillation was significantly slower in the amiodarone group (107 +/- 21) than in the control group (138 +/- 24 beats per minute, p < 0.01). The duration of atrial fibrillation in the amiodarone group (1.1 +/- 1.2 hours) was significantly shorter than that in the control group (3.2 +/- 1.3 hours, p = 0.01). The two groups had no significant differences in incidence of major morbidity (8 of 74 versus 8 of 76 in amiodarone and control groups, respectively) or mortality (4 of 74 versus 5 of 76). However, the control group had significantly longer intensive care unit stays (132 +/- 24 versus 111 +/- 19 hours, p < 0.01).</AbstractText>Perioperative low-dose intravenous amiodarone significantly reduces the incidence, ventricular rate, and duration of atrial fibrillation after coronary artery bypass grafting. Furthermore, low-dose intravenous amiodarone is well tolerated and does not increase the risk of intraoperative or postoperative complications.</AbstractText> |
4,570 | Prophylaxis of supraventricular and ventricular arrhythmias after coronary artery bypass grafting with low-dose sotalol. | Supraventricular tachyarrhythmia (SVT) commonly occurs shortly after coronary artery bypass grafting (CABG), but ventricular arrhythmias are less documented.</AbstractText>On the 1st postoperative day, 206 consecutive eligible patients were prospectively randomized to a sotalol group (80 mg b.i.d.; n = 103) or a control group without beta-blockade or antiarrhythmic drugs (n = 103).</AbstractText>The SVT incidence (predominantly atrial fibrillation) accounted for 16% in the sotalol group versus 48% (p < 0.00001). Multivariate analysis showed that sotalol reduced the SVT incidence (p < 0.00001, odds ratio, 0.20; 95% confidence interval, 0.09 to 0.42), whereas a lower preoperative left ventricular ejection fraction (p = 0.019) and older age (p = 0.031) were independent risk factors of SVT occurrence. The Holter electrocardiographic analysis (24 hours) demonstrated that sotalol (32 versus 92; p = 0.031) decreased the median number of ventricular events, mostly isolated premature ventricular beats. Neither ventricular proarrhythmia effect nor "torsades de pointes" were detected. Despite strict hemodynamic-based selection, sotalol had to be discontinued in 8 patients (7.8%), for reasons related to asthma in 3 or cardiac reasons in 5.</AbstractText>Oral low-dose sotalol provided considerable and reliable protection in selected nondepressed cardiac function patients, reducing the occurrence of both supraventricular and ventricular arrhythmias after CABG.</AbstractText> |
4,571 | End-tidal carbon dioxide as a noninvasive indicator of cardiac index during circulatory shock. | To document the relationships between cardiac index and end-tidal carbon dioxide tension (PetCO2 during diverse low-flow states of circulatory shock.</AbstractText>Randomized, prospective, controlled studies on animal models of hemorrhagic, septic, and cardiogenic shock.</AbstractText>University-affiliated research laboratory.</AbstractText>Sixteen anesthetized domestic pigs weighing 35-45 kg.</AbstractText>Hemorrhagic shock was induced in five pigs by bleeding followed by reinfusion of shed blood. Septic shock was induced in five pigs by infusion of live Escherichia coli. Cardiogenic shock followed an interval of global myocardial ischemia after inducing and reversing ventricular fibrillation in six pigs.</AbstractText>PetCO2 was continuously measured. Cardiac index was measured intermittently by using conventional thermodilution techniques. Cardiac index was correlated with PetCO2 by polynomial regression and Bland-Altman analyses. PetCO2 was highly correlated with cardiac index during hemorrhagic shock (r2 = .69, p < .01), septic shock (r2 = .65, p < .01), and cardiogenic shock (r2 = .81, p < .01). PetCO2 predicted thermodilution cardiac index with bias of -11+/-27 (+/-2 SD) mL/min/kg during hemorrhagic shock, 1.3+/-20.4 (+/- 2 SD) mL/min/kg during septic shock, and -1+/-12 (+/-2 SD) mL/min/kg during cardiogenic shock.</AbstractText>Cardiac output and PetCO2 were highly related in diverse experimental models of circulatory shock in which cardiac output was reduced by >40% of baseline values. Therefore, measurement of PetCO2 is a noninvasive alternative for continuous assessment of cardiac output during low-flow circulatory shock states of diverse causes.</AbstractText> |
4,572 | Cardiopulmonary resuscitation of older, inhospital patients: immediate efficacy and long-term outcome. | To determine the independent effect of advancing age on prognosis after cardiopulmonary resuscitation (CPR).</AbstractText>Retrospective analysis of clinical records of patients who received CPR in a geriatric department equipped with an intensive care unit.</AbstractText>A total of 245 patients (146 men, 99 women; mean age, 70+/-11 yrs) received CPR. Of these, 221 had a cardiocirculatory arrest (CA) in the intensive care unit and 24 had a CA in the general ward of the department. Acute myocardial infarction was the most frequent admission diagnosis.</AbstractText>CPR according to standard guidelines in all cases.</AbstractText>Immediate, short-term (hospital discharge), and long-term (median follow-up, 31.5 months; range, <1-124 months) survival. Older patients had a lower immediate survival (<70 yrs [72/137] 52.6% vs. > or =70 yrs [43/108] 39.4%; p < .05) and, less frequently, ventricular tachycardia/ fibrillation (VT/VF) as a cause of CA. VT/VF bore the lowest immediate mortality rate (19/104; 18.3%) as compared with asystole/complete heart block (66/102; 64.7%) or pulseless electrical activity (40/49; 81.6%; p < .001). Acute myocardial infarction, acute heart failure, hypotension, and occurrence of CA in the intensive care unit were also univariate predictors of unfavorable, immediate prognosis. However, in a multiple logistic analysis model, the mechanism of CA (asystole/complete heart block or pulseless electrical activity vs. VT/VF), acute myocardial infarction, heart failure, and hypotension were independent predictors of unfavorable immediate prognosis, whereas advancing age was not. Similarly, after initially successful CPR, short-term survival was independently associated with acute myocardial infarction, hypotension before CA, initial rhythm at CA, and need for mechanical ventilatory support after CPR, but not with age. Longterm survival (42 patients; 17.2% of the original cohort; median survival, 32 months) was also independent of age, whereas it was negatively associated with heart failure.</AbstractText>Immediate, short- and long-term prognosis after in hospital CPR is independent of age, at least when possible confounders are simultaneously taken into account.</AbstractText> |
4,573 | [Prevention of cardiovascular disease in the elderly]. | PREVENTION OF STROKE: Several preventive strategies have been found to be effective for the prevention of stroke in elderly subjects, including treatment of high blood pressure, oral anticoagulants in case of atrial fibrillation, aspirin for subjects at risk. PREVENTION OF MYOCARDIAL INFARCTION: Anti-hypertension treatment and aspirin for at risk subjects have been proven effective. For elderly subjects who have had a myocardial infarction, beta-blockers and converting enzyme inhibitors are effective in case of altered left ventricular function. The importance of lowering cholesterol levels in the elderly is a subject of debate. In coronary artery disease patients, at least up to the age of 75 years, statins can reduce the risk of a coronary event and stroke. GENERAL MEASURES: Exposure to tobacco smoke and sedentary lifestyle are associated with increased cardiovascular risk in the elderly. Stopping smoking and regular physical exercise should be advised for the elderly. The cardiovascular benefit of hormone replacement therapy after menopause is not clearly established and is the object of ongoing research. |
4,574 | Pitfalls of the concept of incremental specificity used in comparisons of dual chamber VT/VF detection algorithms. | The concepts of incremental specificity and incremental positive predictive accuracy (PPA) have been proposed to measure the success of dual chamber cardioverter defibrillator (ICD) algorithms for tachyarrhythmia detection in improving specificity while maintaining very high sensitivity to detection of episodes of ventricular tachycardia/fibrillation (VT/VF). While dual chamber VT/VF detection algorithms differ substantially among different ICD manufacturers, they all operate as "add-on" features to the single chamber elementary detection algorithms that are based on simple criteria of increased ventricular rate. The incremental specificity and PPA characterize the performance of the dual chamber detection operation in this "add-on" mode, that is within a database of rhythm episodes all meet the simple rate-based criteria. A statistical model of hypothetical devices has been used to demonstrate that the concepts of incremental specificity and PPA are very dependent on the composition of the database used to evaluate a particular dual chamber ICD. Because some sinus tachycardia and supraventricular tachyarrhythmias with regular atrioventricular conduction are more easily discriminated from true VT/VF than other supraventricular tachyarrhythmias, the model shows that rather than the performance of the dual chamber detection functions, the major contributor to the incremental specificity may be the proportion between the "easy" and "difficult" supraventricular episodes. The algorithms used by different ICD manufacturers to detect tachyarrhythmias based on ventricular rate are known to differ substantially in the ability to differentiate true VT/VF from other tachyarrhythmias. Consequently, the databases of rhythms against which the different dual camber ICDs are tested are also different in composition of different types of supraventricular tachyarrhythmias. Therefore, the values of incremental specificity and PPA reported by different manufacturers do not have an equivalent meaning and do not offer a valid comparison of the true performance of different dual chamber ICDs. |
4,575 | P wave dispersion on 12-lead electrocardiography in patients with paroxysmal atrial fibrillation. | The prolongation of intraatrial and interatrial conduction time and the inhomogeneous propagation of sinus impulses have been shown in patients with atrial fibrillation. Recently P wave dispersion (PWD), which is believed to reflect inhomogeneous atrial conduction, has been proposed as being useful for the prediction of paroxysmal atrial fibrillation (PAF). Ninety consecutive patients (46 men, 44 women; aged 55 +/- 13 years) with a history of idiopathic PAF and 70 healthy subjects (42 men, 28 women; mean age 53 +/- 14 years) were studied. The P wave duration was calculated in all 12 leads of the surface ECG. The difference between the maximum and minimum P wave duration was calculated and this difference was defined as P wave dispersion (PWD = Pmax-Pmin). All patients and controls were also evaluated by echocardiography to measure the left atrial diameter and left ventricular ejection fraction (LVEF). There was no difference between patients and controls in gender (P = 0.26), age (P = 0.12), LVEF (66 +/- 4% vs 67 +/- 5%, P = 0.8) and left atrial diameter (36 +/- 4 mm vs 34 +/- 6 mm, P = 0.13). P maximum duration was found to be significantly higher in patients with a history of PAF (116 +/- 17 ms) than controls (101 +/- 11 ms, P < 0.001). P wave dispersion was also significantly higher in patients than in controls (44 +/- 15 ms vs 27 +/- 10 ms, P < 0.001). There was a weak correlation between age and P wave dispersion (r = 0.27, P < 0.001). A P maximum value of 106 ms separated patients with PAF from control subjects with a sensitivity of 83%, a specificity of 72%, and a positive predictive accuracy of 79%. A P wave dispersion value of 36 ms separated patients from control subjects with a sensitivity of 77%, a specificity of 82%, and a positive predictive accuracy of 85%. In conclusion, P maximum duration and P wave dispersion calculated on a standard surface ECG are simple ECG markers that could be used to identify the patients with idiopathic paroxysmal atrial fibrillation. |
4,576 | High rate atrial tachyarrhythmia detections in implantable pulse generators: low incidence of false-positive detections. The PA Clinical Trial Investigators. | Some newer pulse generators have enhanced diagnostic features that provide information on the frequency, date, time of onset, and duration of atrial and/or ventricular tachyarrhythmias. However, the sensitivity and specificity of device-based atrial tachyarrhythmia detections may vary and depend, in part, on lead position and selected programming parameters. The prevalence of inappropriate detections of paroxysmal atrial fibrillation (PAF) was investigated in 97 patients who received a Thera DR pacemaker 3 months prior to a planned AV node ablation. Patients were randomized to no atrial or to rate adaptive atrial pacing therapy and followed for 3 months. Following a total AV node ablation, patients were randomized to DDDR versus VDD pacing and followed for 1 year. The high rate atrial episode diagnostic feature was used for detection of PAF and the diagnostic data were retrieved during follow-up visits. Criteria were developed to identify oversensing due to near-field P wave detections, far-field R wave detections, or competitive atrial pacing as causes of false-positive atrial tachyarrhythmia detections. A total of 1,636 detections of PAF were recorded in patients preablation. Only 48 episodes (2.9%) were characterized as false-positive detections; 25 episodes (1.5%) were classified as oversensing, and 23 episodes (1.4%) were classified as competitive atrial pacing. A total of 3,061 detections of PAF were recorded postablation. Only four episodes (0.1%) were classified as oversensing. Thus, the diagnostic atrial tachyarrhythmia detection feature in newer pacemakers is an effective method for evaluating the time course of PAF in patients with implantable pulse generators. |
4,577 | [Digitalis intoxication during the neonatal period: role of dehydration]. | Despite the great progress which has been made in the treatment of acute digitalis intoxication by digoxin-immune Fab, it still remains a severe complication of cardiotonic therapy.</AbstractText>A neonate with ventricular septal defect and large left-to-right shunt was treated with digitalis and diuretics at the usual starting doses. An intensive phototherapy was also required because of a hyperbilirubinemia due to glucose-6-phosphate dehydrogenase deficiency. Toxic digoxin accumulation (plasma level 14 ng/mL) was diagnosed three days after the initiation of treatment by the presence of sinus bradycardia and bursts of ventricular fibrillation. Intravenous administration of digoxin-specific antibody Fab fragments (Digidot) was effective, with a rapid improvement of the digitalis poisoning.</AbstractText>Because of the particularities concerning drug distribution, metabolism and elimination of drugs in the neonatal period, the digoxin therapeutic index is narrow. This case report suggests the involvement of phototherapy and diuretics, which might induce a significant decrease in extracellular water and drug distribution volumes, ultimately promoting the occurrence of an intoxication.</AbstractText> |
4,578 | [Utilization of implantable ventricular defibrillators (with an analysis of the value of antiarrhythmics in the treatment of potentially fatal ventricular arrhythmias]. | During the past 15 years, the efficacy of antiarrhythmic drugs has been investigated for reducing sudden cardiac death in patients at high risk of arrhythmia. Whereas the benefits of beta-blocker therapy are well established, a reduction in mortality with other antiarrhythmic drugs remains unproved and in some cases, there is evidence of increased mortality with class I and some class III agents. At the same time, the development of the automatic implantable cardioverter-defibrillator has been one of the spectacular achievements in cardiology. It has altered the therapeutic landscape for patients with symptomatic ventricular tachycardia or cardiac arrest. In these patients, the automatic implantable defibrillator is clearly first line therapy, as recognized by the international scientific cardiac societies guidelines. |
4,579 | Life threatening coronary artery spasm in childhood Kimura's disease. | A 13 year old boy is described with hypereosinophilia associated with Kimura's disease, who showed repeated life threatening syncopal attacks during daily activities or at rest. Coronary arteriography demonstrated small aneurysms with irregular vessel walls of both coronary arteries, and the absence of organic stenotic lesions. Infusion of a minimal dose of ergonovine into the right coronary artery induced severe spasm of the vessel. Ventricular fibrillation recurred even after administration of nifedipine and isosorbide was started, but was completely inhibited by prednisolone. |
4,580 | The role of beta-blockers in preventing sudden death in heart failure. | Sudden death accounts for one third to one half of the deaths in patients with heart failure. Recent studies using beta-adrenergic blockers in patients with reduced systolic function and heart failure symptoms have shown significant reductions in overall mortality rates. This article discusses the role of beta-blockers in preventing sudden death in these patients. Six large beta-blocker trials in patients with heart failure have been published to date, with a combined relative risk reduction for sudden death of 38% (confidence interval [CI] 0.53-0.23; P < .001). Although dependent on a nonmechanistic definition of sudden death, the clinical trials of beta-blockers to date have shown that they significantly reduce the risk of sudden death in patients with heart failure. Future studies are required to define the role of other heart failure therapies in the context of this new standard of care. |
4,581 | Atrium as a source of brain natriuretic polypeptide in patients with atrial fibrillation. | Plasma brain natriuretic polypeptide (BNP) levels have been used as biochemical markers of systolic left ventricular (LV) dysfunction. Although in vitro studies have shown the existence of BNP messenger RNA in the atria, the main production site of BNP is believed to be the ventricle. The hypothesis that the atrium could be a source of BNP was examined in patients with lone atrial fibrillation (AF), the most common type of sustained arrhythmia.</AbstractText>We studied 16 controls and 21 patients with lone AF. Plasma samples for BNP were selectively and serially obtained from the aorta, anterior interventricular vein (AIV), and coronary sinus (CS). Atrial natriuretic polypeptide (ANP) levels were also measured to determine whether the CS samples contained significant amounts of atrial venous drainage. Of the 3 sample locations, the CS had the greatest ANP levels, confirming transcatheter sampling position accuracy. BNP levels were significantly greater in the CS than AIV in the patients with AF (279 +/- 226 v 126 +/- 97 pg/mL; P < .01). Consequently, plasma BNP levels were also greater in the patients with AF than controls (103 +/- 90 v 5 +/- 2 pg/mL; P < .001). LV ejection fraction was significantly less in patients with AF than control patients. Atrial production of BNP decreased significantly after successful DC cardioversion of AF in the 5 restudied patients (182 +/- 139 v 59 +/- 64 pg/mL; P < .05).</AbstractText>The data suggest that AF is a condition in which BNP is produced in the atrium itself.</AbstractText> |
4,582 | Electrophysiological changes of angiotensin-converting enzyme inhibition after myocardial infarction. | To investigate whether prevention of remodeling would translate into a more stable electrophysiological profile, the investigators randomized 56 patients to treatment with angiotensin-converting enzyme (ACE) inhibition or placebo for 3 months after myocardial infarction. Programmed electrical stimulation revealed no significant differences in inducibility of monomorphic sustained ventricular tachycardia (VT), whereas ventricular fibrillation (VF) tended to be lower in the ACE-inhibitor group. Effective refractory periods were consistently longer, and dispersion of refractoriness was significantly shorter in the ACE-inhibitor group. The investigators conclude that in this small patient group ACE inhibition may mildly add to a more stable electrophysiological profile. |
4,583 | Bone marrow granulomas possibly associated with amiodarone. | Amiodarone is a class III antiarrhythmic agent that is effective in treating different types of cardiac dysrhythmias. It was approved only for treatment of life-threatening ventricular dysrhythmias refractory to other therapy; however, its use for atrial dysrhythmias such as atrial fibrillation is well accepted. Adverse effects associated with amiodarone include pulmonary, hepatic, thyroid, ocular, and neurologic toxicities. Our patient experienced intermittent fever, night sweats, and fatigue while taking the drug for treatment of atrial fibrillation. Bone marrow biopsy showed granuloma formation after 17 months of therapy with amiodarone. Amiodarone was discontinued due to significant hypotension and shortness of breath. To our knowledge, this is the third case report of granuloma formation in bone marrow possibly associated with this agent. |
4,584 | Dofetilide, a new class III antiarrhythmic agent. | Dofetilide is a new antiarrhythmic agent recently approved for conversion and maintenance of sinus rhythm in patients with atrial fibrillation (AF) and atrial flutter (AFl). It is a class III antiarrhythmic that works by selectively blocking the rapid component of the delayed rectifier outward potassium current. Dofetilide prolongs the effective refractory period in accessory pathways, both anterograde and retrograde. This can be seen on the electrocardiogram through a dose-dependent prolongation of the QT and QTc intervals, with parallel increases in ventricular refractoriness. Approximately 80% of drug is excreted in urine, so dosing must be based on creatinine clearance. The elimination half-life is approximately 10 hours. In clinical trials dofetilide was superior to flecainide in converting patients with AFl to normal sinus rhythm (NSR; 70% vs 9%, p<0.01). It also was more effective than sotalol in converting patients with both AF and AFl to NSR (29% vs 6%, p<0.05) and maintaining them in NSR for up to 1 year. Most patients converted within 24-36 hours. Dofetilide has a favorable risk:benefit profile. Torsades de pointes is the most serious side effect; it occurs in 0.3-10.5% of patients and is dose related. To minimize the risk of induced arrhythmia, patients who start or restart the drug should be hospitalized a minimum of 3 days for creatinine clearance measurements, continuous electrocardiographic monitoring, and cardiac resuscitation, if necessary. |
4,585 | Prediction of major arrhythmic events and sudden cardiac death in dilated cardiomyopathy. The Marburg Cardiomyopathy Study design and description of baseline clinical characteristics. | The Marburg Cardiomyopathy Study (MACAS) is a prospective observational study designed to determine the value of the following potential non-invasive arrhythmia risk predictors in more than 200 patients with idiopathic dilated cardiomyopathy (IDC) over a 5-year follow-up period: New York Heart Association functional class, left ventricular end-diastolic diameter and ejection fraction, left bundle branch block and atrial fibrillation on ECG, QTc and JTc-dispersion on 12-lead ECG, abnormal time-domain analysis and spectral turbulence analysis of the signal-averaged ECG, ventricular arrhythmias and heart-rate variability on 24-hour Holter ECG, baroreflex sensitivity, and microvolt T wave alternans during exercise. This report describes the rationale of MACAS as well as the clinical characteristics of the first 236 patients enrolled between March 1996 and October 1999. The prognostic significance of the potential arrhythmia risk predictors in MACAS will be determined by multivariate Cox analysis at the end of 5-year follow-up. Primary endpoints are total mortality and major arrhythmic events defined as sustained ventricular tachycardia, ventricular fibrillation or sudden cardiac death. The results of MACAS will have important implications for the design of future studies evaluating the role of prophylactic defibrillator therapy in idiopathic dilated cardiomyopathy. |
4,586 | Effects on infarct size and on arrhythmias by controlling reflow after myocardial ischaemia in pigs. | Part of the myocardial damage after an ischaemic period might be related to the reperfusion conditions. Many abrupt changes occurring in the heart during reperfusion may add to the damage during the preceding ischaemic period, and increase in infarct size. In this study we tested the hypothesis that infarct size and occurrence of ventricular arrhythmias might be reduced by restricting reflow after an ischaemic period. Seventeen pigs underwent 45 min of total occlusion of the left anterior descending coronary artery with an hydraulic occluder. In the intervention group reperfusion was restricted to 50% of baseline during the first minute, to 100% during the next minute, kept constant for 1 min, and thereafter allowed to increase by 50% of baseline flow every minute until free reflow. In the control group reflow was not restricted. Arrhythmias were recorded. After 2.5 h of reperfusion the heart was excised. Infarct size was measured by using triphenyltetrazolium chloride (delineation of necrosis), fluorescent microspheres (delineation of area at risk) and planimetry. No reduction in infarct size (% of area at risk) was found between the intervention group and the control group (75.9 +/- 5.3% vs. 72.4 +/- 4.3%). The incidence of ventricular arrhythmias and ventricular fibrillation were not found to be different between the groups during reperfusion. Hemodynamic parameters were not significantly different between the two groups. Our data indicate that no substantial protection against myocardial infarct or ventricular arrhythmias could be achieved by controlling reflow using the present protocol after a period of myocardial ischaemia in pigs. Accordingly, our data do not support the notion that control of reflow may be beneficial when treating coronary artery occlusion with percutaneous coronary angioplasty (PCA). |
4,587 | Do patients with suspected heart failure and preserved left ventricular systolic function suffer from "diastolic heart failure" or from misdiagnosis? A prospective descriptive study. | To characterise the clinical features of patients with suspected heart failure but preserved left ventricular systolic function to determine if they have other potential causes for their symptoms rather than being diagnosed with "diastolic heart failure."</AbstractText>Prospective descriptive study.</AbstractText>Outpatient based direct access echocardiography service.</AbstractText>159 consecutive patients with suspected heart failure referred by general practitioners.</AbstractText>Symptoms (including shortness of breath, ankle oedema, and paroxysmal nocturnal dyspnoea) and history of coronary heart disease and chronic pulmonary disease. Transthoracic echocardiography, body mass index, pulmonary function tests, and electrocardiography.</AbstractText>109 of 159 participants had suspected heart failure in the absence of left ventricular systolic dysfunction, valvular heart disease, or atrial fibrillation. Of these 109, 40 were either obese or very obese, 54 had a reduction in forced expiratory volume in 1 second to </=70%, and 97 had a peak expiratory flow rate </=70% of normal. Thirty one patients had a history of angina, 12 had had a myocardial infarction, and seven had undergone a coronary artery bypass graft. Only seven patients lacked a recognised explanation for their symptoms.</AbstractText>For most patients with a diagnosis of heart failure but preserved left ventricular systolic function there is an alternative explanation for their symptoms-for example, obesity, lung disease, and myocardial ischaemia-and the diagnosis of diastolic heart failure is rarely needed. These alternative diagnoses should be rigorously sought and managed accordingly.</AbstractText> |
4,588 | Suicide by ingestion of a CCA wood preservative. | Chromated-copper-arsenate (CCA) is a compound used worldwide for wood preservation. Occupational hazards from chronic exposure to CCA are well known, but acute ingestion of CCA wood preservative is very rare. We describe a case of suicide by ingestion of a CCA wood preservative. A 33-year-old man attempted suicide by ingesting an unknown liquid, later identified as a CCA wood preservative, 75 min before his arrival in the emergency department. He was in severe respiratory distress, drooling, tachycardic, and hypotensive. There was an orange color on the palms of both hands. Severe, green colored burns of the buccal mucosa were observed. He was intubated shortly after arrival. The larynx was edematous, but a 7-mm endotracheal tube was successfully introduced. Blood tests revealed partially compensated metabolic acidosis. The patient deteriorated rapidly; the systolic blood pressure dropped to 70 mmHg, and he passed bloody diarrhea. He developed multiple premature atrial contractions and supraventricular tachycardia, and later in the intensive care unit, refractory ventricular tachycardia and ventricular fibrillation. The patient was declared dead 212 h after his arrival. Unfortunately, postmortem blood levels of heavy metals and autopsy were not performed because of refusal by the family for religious reasons. |
4,589 | Prospective study of early discharge after acute myocardial infarction (SHORT). | To identify, without additional investigation, a large group of myocardial infarction patients at low risk who would qualify for early discharge.</AbstractText>The decision rule was developed in 647 unselected patients with consecutively admitted myocardial infarction, and validated in 825 others. Daily event-rates were calculated for major (death, ventricular fibrillation, recurrent infarction, heart failure, advanced AV-block) and minor (unstable angina and rhythm-abnormalities) cardiac complications.</AbstractText>Patients free from major complications until day 7 (44% of all patients) were found to constitute a very low risk group and thus would qualify for discharge at day 7. Of the 39% of patients with an uncomplicated infarction (low risk) in the validation group, 31% were discharged at day 7, while 8% stayed longer because of non-cardiac co-morbidity, for social reasons or logistic problems. No major adverse event occurred within 7 days after hospital discharge and only 1.8% developed complications within 1 month. The median duration of hospital stay for all in-hospital survivors was 7 days compared to 10 days in the control group.</AbstractText>Prospective application of the early discharge decision rule, based upon simple clinical variables and without the need for additional non-invasive and/or invasive tests, resulted in a significant reduction of hospital stay. The decision rule correctly classified patients into high and low risk groups and appeared feasible and safe. Its efficacy was demonstrated by its ability to identify a large group of post infarction survivors at low risk for complications during follow-up.</AbstractText> |
4,590 | Melatonin scavenges hydroxyl radical and protects isolated rat hearts from ischemic reperfusion injury. | During postischemic reperfusion, free radicals are produced and have deleterious effects in isolated rat hearts. We investigated whether melatonin (MEL) reduces the production of hydroxyl radical (*OH) in the effluent and aids in recovery of left ventricular (LV) function. Hearts were subjected to 30 min of ischemia followed by 30 min of reperfusion. Salicylic acid (SAL) was used as the probe for *OH, and its derivatives 2,5- and 2,3-dihydroxybenzoic acid (DHBA) were quantified using HPLC. In addition, thiobarbituric acid reactive substances (TBARS) in the myocardium was measured. Plateaus in the measurement of 2,5- and 2,3-DHBA were seen from 3 to 8 min after reperfusion in each group. The group that received 100 microM MEL+ SAL had significantly reduced amounts of 2,5- and 2,3-DHBA by multiple folds, compared to the SAL group. TBARS was significantly decreased in the 100 microM MEL group (1.20+/-0.36 vs 1.85+/-0.10 micromol/g of drug-free group, p<0.001). More importantly, the 100 microM MEL group significantly recovered in LV function (LV developed pressure, +dp/dt, and -dp/dt; 63.0%, 60.3%, and 59.4% in the 100 microM MEL group; 30.2%, 29.7%, and 31.5% in the drug-free group, respectively; p<0.05). Duration of ventricular tachycardia or ventricular fibrillation significantly decreased in the 100 microM MEL group (100 microM MEL, 159+/-67 sec; drug-free, 1244+/-233 sec; p<0.05). As a result of scavenging *OH and reducing the extent of lipid peroxidation, MEL is an effective agent for protection against postischemic reperfusion injury. |
4,591 | Opioid-induced cardioprotection against myocardial infarction and arrhythmias: mitochondrial versus sarcolemmal ATP-sensitive potassium channels. | We examined the role of the sarcolemmal and mitochondrial ATP-sensitive potassium (K(ATP)) channel in a rat model of myocardial infarction after stimulation with the selective delta(1)-opioid receptor agonist TAN-67. Hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Infarct size was expressed as a percentage of the area at risk. TAN-67 significantly reduced infarct size/area at risk (29.6 +/- 3.3) versus control (63. 1 +/- 2.3). The sarcolemmal-selective K(ATP) channel antagonist HMR 1098, administered 10 min before TAN-67, did not significantly attenuate cardioprotection (26.0 +/- 7.3) at a dose (3 mg/kg) that had no effect in the absence of TAN-67 (56.3 +/- 4.3). Pretreatment with the mitochondrial selective antagonist 5-hydroxydecanoic acid (5-HD) 5 min before the 30-min occlusion completely abolished TAN-67-induced cardioprotection (54.3 +/- 2.7), but had no effect in the absence of TAN-67 (62.6 +/- 4.1), suggesting the involvement of the mitochondrial K(ATP) channel. Additionally, we examined the antiarrhythmic effects of TAN-67 in the presence or absence of 5-HD and HMR 1098 during 30 min of ischemia. Control animals had an average arrhythmia score of 10.40 +/- 2.41. TAN-67 significantly reduced the arrhythmia score during 30 min of ischemia (2.38 +/- 0. 85). 5-HD and HMR 1098 in the absence of TAN-67 produced an insignificant decrease in the arrhythmia score (8.80 +/- 2.56 and 4. 20 +/- 1.07, respectively). 5-HD administration before TAN-67 treatment abolished its antiarrhythmic effect (4.71 +/- 1.11). However, HMR 1098 did not abolish TAN-67-induced protection against arrhythmias (1.67 +/- 0.80). These data suggest that delta(1)-opioid receptor stimulation is cardioprotective against myocardial ischemia and sublethal arrhythmias and suggest a role for the mitochondrial K(ATP) channel in mediating these cardioprotective effects. |
4,592 | Homozygotes for a R869G mutation in the beta -myosin heavy chain gene have a severe form of familial hypertrophic cardiomyopathy. | Familial Hypertrophic Cardiomyopathy (FHC) is an autosomal dominant disease characterised by ventricular hypertrophy, with predominant involvement of the interventricular septum. It is a monogenic disease with a high level of genetic heterogeneity (nine genes and more than 110 mutations reported so far). We describe a family with a new R869G mutation in the beta -myosin heavy chain gene (MYH7). This mutation was found in the heterozygous status in both parents and in the homozygous status in the two children. A haplotype analysis on the MYH7 locus with microsatellite markers showed that the same haplotype is transmitted within the family, suggesting a founder effect. Clinically, the father was asymptomatic with mild left ventricular hypertrophy on echocardiography. The mother had a mild form of hypertrophic cardiomyopathy and remained asymptomatic until 60 years old when an atrial fibrillation occurred. For the two children, clinical diagnosis was performed at 12 and 8 years and atrial fibrillation occurred at 17 years. For both children, the evolution was characterized by left ventricle (LV) systolic dysfunction and a severe dilatation of the left atrium before 40 years of age.</AbstractText>In this family, a new R869G mutation in the MYH7 gene was found. Interestingly, a mutation was found at the homozygous status for the first time in FHC. This finding suggests that this particular mutation is compatible with life, but for homozygous subjects, age at onset of symptoms was earlier and the disease much more severe than in the heterozygous subjects, suggesting a gene-dose effect.</AbstractText>Copyright 2000 Academic Press.</CopyrightInformation> |
4,593 | Rate-dependency of action potential duration and refractoriness in isolated myocytes from the rabbit AV node and atrium. | During atrial fibrillation, ventricular rate is determined by atrioventricular nodal (AVN) conduction, which in part is dependent upon the refractoriness of single AVN cells. The aims of this study were to investigate the rate-dependency of the action potential duration (APD) and effective refractory period (ERP) in single myocytes isolated from the AV node and atrium of rabbit hearts, using whole cell patch clamping, and to determine the contribution of the 4-aminopyridine (4-AP)-sensitive current, I(TO1)to these relationships in the two cell types. AVN cells had a more positive maximum diastolic potential (-60+/-1 v-71+/-2 mV), lower V(max)(8+/-2 v 144+/-17 V/s) and higher input resistance [420+/-46 v 65+/-7 MOmega (mean+/-s.eP<0.05 n=9-33)], respectively, than atrial myocytes. Stepwise increases in rate from 75 beats/min caused activation failure and Wenckebach periodicity in AVN cells (at around 400 beats/min), but 1:1 activation in atrial cells (at up to 600 beats/min). Rate reduction from 300 to 75 beats/min shortened the ERP in both cell types (from 155+/-7 to 135+/-11 ms in AVN cells [P<0.05, n=6] and from 130+/-8 to 106+/-7 ms in atrial cells [P<0.05, n=10]). Rate increase from 300 to 480 and 600 beats/min shortened ERP in atrial cells, by 12+/-4% (n=8) and 26+/-7% (n=7), respectively (P<0.05). By contrast, AVN ERP did not shorten at rates >300 beats/min. In atrial cells, rate reduction to 75 beats/min caused marked shortening of APD(50)(from 51+/-6 to 29+/-6 ms, P<0. 05). 4-AP (1 m m) significantly prolonged atrial APD(50)at 75 beats/min (P<0.05, n=7), but not at 300 or 400 beats/min. In AVN cells, in contrast, there was less effect of rate change on APD, and 4-AP did not alter APD(50)at any rate. 4-AP also did not affect APD(90)or ERP in either cell type. In conclusion, a lack of ERP-shortening at high rates in rabbit single AVN cells may contribute to ventricular rate control. I(TO1)contributed to the APD(50)rate relation in atrial, but not AVN cells and did not contribute to the ERP rate relation in either cell type. |
4,594 | Reduced ventricular response irregularity is associated with increased mortality in patients with chronic atrial fibrillation. | BACKGROUND-Variations in the ventricular response interval (VRI) during atrial fibrillation (AF) may be reduced in patients with adverse clinical outcomes. The properties of VRI dynamics associated with prognosis remain undetermined. METHODS AND RESULTS-In 107 patients with chronic AF (age, 64+/-9 years), we analyzed a 24-hour ambulatory ECG for VRI variability (SD, SD of successive differences, and SD of 5-minute averages) and VRI irregularity (Shannon entropy of histogram, symbolic dynamics, and approximate entropy of beat-to-beat and minute-to-minute fluctuations [ApEn(b-b) and ApEn(m-m)]). During a follow-up period of 33+/-16 months, 18 patients died (17%), 9 from cardiac causes, 7 from fatal strokes, and 2 from malignancies. Reductions in all VRI variability and irregularity measures were associated with an increased risk for cardiac death but not for fatal stroke. A significant association with cardiac death was also found for ejection fraction (relative risk, 1.10; 95% confidence interval [CI], 1.04 to 1.17, per 1% decrement) and ischemic AF (relative risk, 6.52; 95% CI, 1.62 to 26. 3). After adjustment for these clinical variables, all irregularity measures except symbolic dynamics had predictive value (relative risks [95% CIs] per 1SD decrement: Shannon entropy of histogram, 2. 03 [1.14 to 3.61]; ApEn(b-b), 1.72 [1.14 to 2.60]; and ApEn(m-m), 1. 90 [1.03 to 3.52]); however, the predictive power of variability measures was no longer significant. When the patients were stratified with the 33rd and 67th percentile values of ApEn(b-b) (1. 83 and 1.94, respectively), the 5-year cardiac mortality rates for the upper, middle, and lower tertiles were 0%, 13%, and 43%, respectively (log-rank test, P=0.04). CONCLUSIONS-Reduced VRI irregularity in a 24-hour ambulatory ECG has an independent prognostic value for cardiac mortality during long-term follow-up in patients with chronic AF. |
4,595 | Increased sympathetic activity after atrioventricular junction ablation in patients with chronic atrial fibrillation. | The aim of this study was to determine the changes in sympathetic nerve activity (SNA) after atrioventricular junction (AVJ) ablation in patients with chronic atrial fibrillation (AF).</AbstractText>Polymorphic ventricular tachycardia (PMVT) has been reported after AVJ ablation in patients paced at a rate of < or =70 beats/min. We hypothesized that AVJ ablation results in sympathetic neural changes that favor the occurrence of PMVT and that pacing at 90 beats/min attenuates these changes.</AbstractText>Sympathetic nerve activity, 90% monophasic cardiac action potential duration (APD90), right ventricular effective refractory period (ERP) and blood pressure measurements were obtained in 10 patients undergoing AVJ ablation. Sympathetic nerve activity was analyzed at baseline and during and after successful AVJ ablation for at least 10 min. Data were also collected after ablation at pacing rates of 60 and 90 beats/min. The APD90 and ERP were measured before and after AV block during pacing at 120 beats/min.</AbstractText>Sympathetic nerve activity increased to 134 +/- 16% of the pre-ablation baseline value (p < 0.01) after successful AVJ ablation plus pacing at 60 beats/min and decreased to 74 +/- 8% of baseline (p < 0.05) with subsequent pacing at 90 beats/min. Both APD90 and ERP increased significantly.</AbstractText>1) Ablation of the AVJ followed by pacing at 60 beats/min is associated with an increase in SNA. 2) Pacing at 90 beats/min decreases SNA to or below the pre-ablation baseline value. 3) Cardiac APD and ERP increase after AVJ ablation. The increase in SNA, along with the prolongation in APD, may play a role in the pathogenesis of ventricular arrhythmias that occur after AVJ ablation.</AbstractText> |
4,596 | [Aortic valve replacement for aortic valve stenosis due to congenital bicuspid aortic valve with abnormal positioning of coronary orifice, pseudotendon, and persistent left superior vena cava, report of a case]. | A patient was a 65-year-old female who had a complaint of palpitation was diagnosed aortic valve stenosis due to congenital bicuspid aortic valve with pseudotendon by the echocardiographic examination. We suspected left single coronary artery by the aortography and the coronary artery angiography. Aortic valve replacement and resection of pseudotendon was performed with Carbomedics supra-annular aortic valve (21 A). During surgery, persistent left superior vena cava was detected. High-posterior take-off right coronary artery was casually detected at aortic closure. Ventricular fibrillation due to insufficient supply of cardioplegic solution at right coronary area frequently occurred after cardio-pulmonary bypass and percutaneous cardiopulmonary support was required. The patient was discharged 32 days after the operation. Preoperative and intraoperative evaluation was important in the case of aortic valvular disease. |
4,597 | [A case of aconitine poisoning saved with cardiopulmonary bypass]. | "Torikabuto" is a kind of plant which contains deadly poison. Its ingredient is aconitine alkaloids. We report a case of aconitine poisoning with fatal arrhythmia and acute pulmonary edema who was saved with cardio pulmonary bypass. A 41-year-old male ate to mistake "Torikabuto" for wild plant. He developed symptoms of dysarthria and admitted to our hospital. He developed ventricular tachycardia and fibrillation soon after his admission. Then he developed cardiogenic shock. He was resuscitated and supported with a percutaneous cardio pulmonary bypass. Ventricular tachycardia disappeared 24 hours after admittion. About 1 week later, cardio pulmonary bypass was terminated and about 3 months later, he discharged from our hospital. |
4,598 | Phase II study of paclitaxel and epirubicin as first-line treatment in patients with metastatic nonsmall cell lung carcinoma. | The combination of paclitaxel and epirubicin has shown a favorable interaction in patients with advanced breast carcinoma. Therefore the efficacy and toxicity of this regimen was evaluated in a Phase II study of patients with metastatic nonsmall cell lung carcinoma (NSCLC).</AbstractText>Thirty-two chemotherapy-naive patients with AJCC Stage IV NSCLC and an Eastern Cooperative Oncology Group performance status of 0-1 were entered into the study. Patients received epirubicin, 90 mg/m(2), followed by paclitaxel, 175 mg/m(2) by 3-hour infusion, on Day 1. The treatment was repeated every 3 weeks. Granulocyte-colony stimulating factor (G-CSF) was not used routinely.</AbstractText>A total of 116 treatment cycles was delivered. All patients could be assessed for response, toxicity, and survival. There were 16 partial responses and no complete responses, giving rise to an overall response rate of 50% (95% confidence interval, 31. 9-68.1%). The median time to progression in responders was 7 months. The median survival was 8 months, and the 1-year survival rate was 37%. World Health Organization Grade 4 neutropenia occurred in 69% of patients, but could be managed easily with G-CSF, which was used in 35% of cycles. Cumulative peripheral neuropathy was the main nonhematologic toxicity and was observed in 7 of 8 patients who received 6 treatment courses (Grade 2-3 in 3 cases) and in 6 of 11 patients who received 4 cycles (Grade 2 in 2 patients). One patient died shortly after the first course of chemotherapy from a ventricular arrhythmia.</AbstractText>The combination of paclitaxel and epirubicin was found to be effective and well tolerated in chemotherapy-naive patients with metastatic NSCLC and warrants further evaluation in a multicenter trial of a larger number of patients. Careful cardiac evaluation before treatment is indicated.</AbstractText>Copyright 2000 American Cancer Society.</CopyrightInformation> |
4,599 | Amiodarone for rapid cardioversion of chronic atrial tachyarrhythmia? | Electrical cardioversion of atrial tachyarrhythmia has disadvantages, such as the need for general anaesthesia, skin burns and thoracic pain. Pharmacodynamic cardioversion is without these side effects, but the reports of the efficacy of the treatment vary a lot. Amiodarone has been the only drug so far reported to give a combination of high efficacy and low frequency of serious side effects such as ventricular tachycardia and shock. The purpose of the present study was to assess the effect of amiodarone on chronic atrial tachycardia. Seventeen patients with chronic atrial fibrillation or flutter were given an oral dose of 30 mg/kg amiodarone. Serial blood tests after amiodarone ingestion were taken to document absorption. Patients, who did not convert to sinus rhythm within 24 hr were treated by electrical cardioversion. No patients converted pharmacodynamically to sinus rhythm. Twelve patients (71%) reached the recommended serum concentration of amiodarone (2-2.5 mg/l, median 2.4 mg/l, range 0.96-4.7). The concentration of desethylamiodarone remained low (<0.2 mg/l), and there were no objective or subjective side effects following the treatment. Sixteen patients (94%) were converted to sinus rhythm the day after by electrical cardioversion without complications. A single high dose of amiodarone is a safe but ineffective method of converting chronic atrial fibrillation and flutter, and may be used as adjuvant therapy in combination with electrical cardioversion. |
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