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  • 1
    ISSN: 1572-8595
    Keywords: hemochromatosis ; syncope ; polymorphic ventricular tachycardia ; ventricular fibrillation ; electrophysiologic study ; nuclear magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Hemochromatosis has been associated with atrial tachyarrhythmias and congestive heart failure as a consequence of dilated or restrictive cardiomyopathy. Inducible ventricular fibrillation has not been previously described. Methods and Results: An electrophysiologic study was conducted in a woman after two episodes of syncope. Polymorphic ventricular tachycardia (PMVT) and ventricular fibrillation (VF) were induced with ventricular programmed stimulation. Magnetic resonance imaging demonstrated signal loss in the liver consistent with hemochromatosis, but normal cardiac size and function. Hematologic studies supported a diagnosis of hemochromatosis. Conclusion: Cardiac hemochromatosis may be associated with serious ventricular arrhythmias.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8595
    Keywords: ventricular fibrillation ; monophasic action potential ; ventricular repolarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Introduction: Shocks given during the vulnerable period of cardiac repolarization may induce ventricular fibrillation (VF). However, the relationship of the vulnerable period and the monophasic action potential (MAP) has not yet been reported in humans. The purpose of this study was, therefore, to determine how the monophasic action potential recorded from the right ventricle correlates with inducibility of VF using T wave shocks during ventricular pacing. Methods: Eleven patients undergoing implantable cardioverter defibrillator (ICD) implantation had a MAP catheter positioned in the right ventricle (RV). The local monophasic action potential duration at 90% repolarization (MAP90) duration was measured during pacing at 400 ms. VF induction was attempted by pacing at 400 ms for 10 cycles and then giving a 1.0 joule monophasic T wave shock at varying coupling intervals (CI) to the last paced stimulus. The maximum and minimum CI that induced VF were determined and mapped in relation to the MAP90 recording. Results: The average paced MAP duration was 275 ± 20ms. The minimum and maximum CI to induce VF were 255 ± 24ms and 325 ± 36ms respectively. This ranged from 93% to 118% of the MAP90 duration but because of delay in conduction time to the MAP catheter, shocks that induced ventricular fibrillation occurred between 74% and 99% of local repolarization time. Conclusion: VF is inducible with low energy T wave shocks falling during the last 25% of the right ventricular MAP90 recording. This corresponds with VF initiation during phase III repolarization.
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  • 3
    ISSN: 1572-8595
    Keywords: complete atrioventricular block ; pacemaker--defibrillator interaction ; ventricular fibrillation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A well described interaction between an antibradycardia pacemaker and a ventricular defibrillator is sensing of pacemaker stimuli by the ventricular defibrillator. This report describes an interaction between an atrial demand pacemaker and a ventricular defibrillator that resulted in ventricular asystole and polymorphic ventricular tachycardia. In this case, the ventricular defibrillator sensed atrial pacing stimuli when complete atrioventricular block with a slow ventricular escape rate developed. Defibrillator-based ventricular demand pacing was inhibited, resulting in prolonged periods of ventricular asystole, polymorphic ventricular tachycardia, and multiple defibrillator shocks. Ventricular defibrillator sensing of atrial pacemaker stimuli in the setting of complete atrioventricular block and ventricular asystole cannot be simulated during defibrillator implantation when atrioventricular conduction is intact. Therefore, a pacemaker programmed to atrial demand pacing in a patient with a ventricular defibrillator can result in inappropriate inhibition of ventricular pacing in the setting of complete heart block. Furthermore, this interaction can be avoided with a dual-chamber pacing ventricular defibrillator.
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  • 4
    ISSN: 1572-8595
    Keywords: implantable defibrillator ; implantation approaches ; cost ; ventricular tachycardia ; ventricular fibrillation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent technological advances in implantable defibrillator systems(ICD) have changed implantation approaches. The aim of this study was toinvestigate the influence of these improvements on procedure times,implant-related charges, patient recovery, and morbidity. Ninety-sixconsecutive patients undergoing implantation of a nonthoracotomy ICD werestudied. Implantation was performed under general anesthesia with thegenerator placed abdominally in 22 patients (group I) and pectorally in 40patients (group II). Thirty-four patients underwent pectoral implantationusing conscious sedation (group III). Groups were comparable with respect toclinical variables. Implantation duration and total procedure duration wereshorter in group III (67 ± 21 minutes and 117 ± 30 minutes)when compared with group I (100 ± 25 minutes and 157 ± 39minutes) and group II (86 ± 24 minutes and 153 ± 34 minutes, P〈 0.05). Patients in group III did not require admission to thePost-Anesthesia Care Unit. In contrast, patients in groups I and II spent 92± 28 minutes and 91 ± 31 minutes in the Post-Anesthesia CareUnit. Implantation-related charges were reduced in patients having pectoralimplantation using conscious sedation ($1451 ± 217 vs.$2354 ± 550 and $2796 ± 384, P 〈 0.05).Patients in group III had a lower frequency of postoperative oral analgesicuse (3.2 ± 2.7 doses, P 〈 0.05) and a shortened postoperative length of stay (1.9 ± 1.6 days, P 〈 0.05) when compared withgroups I (5.7 ± 4.0 doses and 3.3 ± 1.4 days) and II (5.2± 3.5 doses and 2.6 ± 1.1 days). The overall complication ratewas low (6.3%), with no differences between groups. Advances in ICDtechnology have simplified implantation, leading to shorter, less painful,and less expensive procedures.
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  • 5
    ISSN: 1572-8595
    Keywords: ventricular tachycardia ; ventricular fibrillation ; acute myocardial ischemia ; sudden coronary death ; myocardial reentry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intramural and epicardial composite electrograms, signal-averaged orthogonal bipolar electrograms across the ischemic zone, and closely-spaced bipolar electrograms from subendocardium, mid-myocardium, and subepicardium were utilized to determine if phase 1B reentry resulted from localized reentry within ischemic mid-myocardium. During the first 10 minutes following coronary ligation, activation delays were largest in ischemic subepicardium, with continuous electrical activity in ischemic epicardium linking a ventricular extrasystole to the preceding beat. During the 15–30 minute period, activation delay observed in ischemic mid-myocardium exceeded activation delay on the epicardial surface. Ventricular extrasystoles were associated with mid-myocardial delays 〉 130 msec. With short-coupled extrasystoles (〈300 msec), electrical activity in ischemic mid-myocardium linked an extrasystole with the preceding beat. Although single extrasystoles with coupling intervals 〉300 msec were also associated with mid-myocardial delays 〉130 msec, most extrasystoles (68%) demonstrated an isoelectric gap 〉20 msec. The data demonstrate an association between delayed activation within ischemic mid-myocardium and phase 1B arrhythmia resulting from (1) localized reentry in ischemic mid-myocardium and (2) a delay-dependent “non-reentrant” mechanism.
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  • 6
    ISSN: 1572-8595
    Keywords: amiodarone ; ventricular tachycardia ; ventricular fibrillation ; guided therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Review of available data suggests that serial drug testing in patients with a history of sustained ventricular tachyarrhythmias using various antiarrhythmic drugs including amiodarone is able to identify subgroups with favorable and unfavorable outcome (patient groups with suppression vs. no suppression of inducibility of VT/VF). These results more likely reflect patient selection rather than drug effects, thus limiting the role of electrophysiologically guided antiarrhythmic therapy to actively modify outcome. All major and actual antiarrhythmic drug trials including an amiodarone arm, have chosen to deliver this drug empirically in both patients with asymptomatic as well as severely symptomatic life-threatening sustained ventricular tachyarrhythmias instead of a guided approach. The empiric approach is therefore adequate until new valid data comparing the empiric with the guided—or the invasive with the non invasive—approach tell us otherwise.
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  • 7
    ISSN: 1572-8595
    Keywords: electrophysiologic study ; ventricular tachycardia ; ventricular fibrillation ; sotalol ; beta-block
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Arrhythmic death can be reduced by antiarrhythmic drugs to a range of 2—4%. Electrophysiologic study by testing noninducibility of ventricular arrhythmia represents the classic method for evaluating the effectiveness of drug therapy. Several clinical studies have shown thaat sotalol suppresses VT induction and prevents arrhythmias recurrences at long term follow-up in 23% to 67% of patients. The efficacy of sotalol EP guided therapy in preventing VT/VF is not necessarily related to prevention of sudden death. In the ESVEM study the superiority of d,l-sotalol to other antiarrhythmic drugs was confirmed. The response to programmed ventricular stimulation was found to be strongly predictive for arrhythmia free state while the failure of sotalol therapy to suppress VT at the EP study was associated with an high recurrence rate (40%). However, EP study failes to predict freedom from sudden death. The beta-blocking activity of racemic sotalol may account for some of the observed survival benefit. Beta-blockers therapy reduces mortality in patients after myocardial infarction primarily by a reduction of sudden death. A reduction of death, worsening heart failure and life threatening ventricular arrhythmias was shown in a recent study on carvedilol. In the prospective study of Steinbeck the EP guided-therapy did not improve the overall outcome when compared to metoprolol. Suppression of inducible arrhythmias by antiarrhythmic drugs was associated with a better outcome. The effectiveness of defibrillator therapy in reducing overall mortality, has been uncertain since great clinical trials have been concluded. MADIT, AVID and CASH trials confirmed the superiority of ICD therapy over antiarrhythmic drugs therapy: ICD should be considered the first choice therapy in post-cardiac arrest patients. The ongoing BEST Trial will give us further responses about the interaction between EP study and metoprolol effect compared to ICD in patients post myocardial infarction also focusing on tolerability and compliance of the beta-blocking therapy in patients with low ejection fraction. In this study will be useful to optimize therapy in patients at high risk of sudden death
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