Risks of developing supraventricular and ventricular tachyarrhythmias after implantation of a cardioverter-defibrillator, and timing the activation of arrhythmia termination therapies

Suppression of sustained ventricular tachyarrhythmias: a comparison of d,l-sotalol with no antiarrhythmic drug treatment

OBJECTIVES

This study evaluates the clinical efficacy of d,l-sotalol in patients with sustained ventricular tachyarrhythmias.

BACKGROUND

D,l-sotalol is an important antiarrhythmic agent to prevent recurrences of sustained ventricular tachyarrhythmias (VT/VF). However, evidence is lacking that an antiarrhythmic agent like d,l-sotalol can reduce the incidence of sustained ventricular tachyarrhythmias in comparison to no antiarrhythmic drug treatment.

METHODS

A prospective study was performed in 146 consecutive patients with inducible sustained ventricular tachycardia or ventricular fibrillation. In 53 patients, oral d,l-sotalol prevented induction of VT/VF during electrophysiological testing and patients were discharged on oral d,l-sotalol (sotalol group). In 93 patients, VT/VF remained inducible and a defibrillator (ICD) was implanted. After implantation of the device patients were randomly assigned to oral treatment with d,l-sotalol (ICD/sotalol group, n=46) or no antiarrhythmic medication (n=47, ICD-only group).

RESULTS

During follow-up, 25 patients (53.2%) in the ICD-only group had a VT/VF recurrence in comparison to 15 patients (28.3%) in the sotalol group and 15 patients (32.6%) in the ICD/sotalol group (p=0.0013). Therapy with d,l-sotalol, amiodarone or metoprolol was instituted in 12 patients (25.5%) of the ICD-only group due to frequent VT/VF recurrences or symptomatic supraventricular tachyarrhythmias. In nine patients, 17% of the sotalol group, an ICD was implanted after VT/VF recurrence, three patients (5.7%) received amiodarone. Total mortality was not different between the three groups.

CONCLUSIONS

D,l-sotalol significantly reduces the incidence of recurrences of sustained ventricular tachyarrhythmias in comparison to no antiarrhythmic drug treatment.

Epicardial cardioverter-defibrillators do not cause postoperative arrhythmias. The CABG Patch Trial Investigators. Coronary Artery Bypass Graft

The CABG Patch Trial is a controlled, multicenter clinical trial that randomized high-risk patients undergoing coronary artery bypass grafting (CABG) to prophylactic implantation of an epicardial implantable cardioverter-defibrillator (ICD) or to no additional treatment, permitting a controlled evaluation of the effect of epicardial ICDs on the incidence of postoperative arrhythmias. We found no significant difference in the development of postoperative arrhythmias between patients who received epicardial ICDs and the control group treated with CABG alone.

Gross and microscopic pathological changes associated with nonthoracotomy implantable defibrillator leads

BACKGROUND

Although the effects of epicardial implantable cardioverter-defibrillator (ICD) leads on underlying cardiac tissue have been reported, the gross and microscopic changes associated with endocardial ICD leads are less well described. This study describes the gross and microscopic changes associated with endocardial ICD leads in humans.

METHODS AND RESULTS

The hearts from 8 patients were examined. At the time of ICD implantation, the patients' mean age was 47+/-11 years, and the left ventricular ejection fraction was 0.24+/-0.10. Four patients had ischemic heart disease, and 4 had dilated cardiomyopathy. Five hearts were examined after transplantation; 3, after death. The electrode-myocardial interfaces were characterized by intense endocardial fibrosis and were remarkably consistent. Each lead was encased by a ring of fibroelastic tissue, and there was fibrosis of the right ventricular myocardium adjacent to the leads. Fibrosis involved the tricuspid valve in 5 patients, and 1 had perforation of the valve by the lead. Microscopically, interstitial fibrosis was adjacent to each lead in the current path of ICD shocks. Acute cell injury was present only in the hearts that had received recent shocks.

CONCLUSIONS

The ICD electrode-myocardial interface is characterized by intense fibrosis. The fibrosis associated with endocardial ICD leads and the cumulative acute damage produced by defibrillation discharges may explain changes in the defibrillation and pacing thresholds and the difficulty of lead extraction that can be encountered with transvenous ICD systems.

Arrhythmias after cardioverter-defibrillator implantation: comparison of epicardial and transvenous systems

Surgery for implantable cardioverter-defibrillators can cause postoperative exacerbation of ventricular and atrial arrhythmias. It is not known whether the techniques of electrode implantation (epicardial vs transvenous) influence the incidence of arrhythmia exacerbation. We reviewed the postoperative course of 229 consecutive patients who received either epicardial (n = 119) or transvenous (n = 110) implantations from 1984 to 1994. Exacerbation of ventricular tachycardia (VT) was defined as an increase in the number of sustained VTs during the postoperative versus the preoperative 2 weeks. Of the entire cohort, 18 patients (8%) developed exacerbation of VT after operation, which was more frequent in patients with epicardial than with transvenous implantations (12% vs 4%, p < 0.03, odds ratio 3.5, 95% confidence interval 1.0 to 13.2). New-onset atrial fibrillation occurred in 15% of patients with epicardial versus 1% of those with transvenous implantations (p = 0.00005, odds ratio 19.4, 95% confidence interval 2.7 to 86.7). These differences persisted after excluding patients with concurrent cardiac surgery. Preoperative occurrence of arrhythmias was the strongest independent predictor for postoperative occurrence (p < 0.01 for VT, p < 0.0001 for atrial fibrillation). Epicardial implantation (p = 0.03) and a history of myocardial infarction (p = 0.04) were independent predictors for postoperative VT exacerbation, whereas epicardial implantation (p < 0.05) and concurrent coronary bypass surgery (p = 0.0001) were independent predictors for postoperative new atrial fibrillation. Perioperative discontinuation of antiarrhythmic drugs did not influence postoperative VT exacerbation. Epicardial implantation was associated with longer length of hospital stay than transvenous implantation (p = 0.0005), independent of age, left ventricular ejection fraction, and concurrent cardiac surgery.

Improved defibrillation threshold with a new epicardial carbon electrode compared with a standard epicardial titanium patch

BACKGROUND

Recent studies show that depending on the type of shock morphology used, 5% to 15% of patients requiring implantable defibrillators cannot be treated with a nonthoracotomy system. In these cases, an epicardial patch-based system becomes necessary. In this study, we investigated a newly developed epicardial carbon electrode as an alternative to a standard epicardial titanium patch.

METHODS AND RESULTS

A tubular epicardial braided carbon electrode of 7F diameter and 14-cm length applied in a U-shape to the epicardium was compared with a standard left ventricular epicardial 15-cm2 titanium mesh patch (CPI Inc). As cathode, a CPI endocardial lead, a Medtronic lead, or a carbon-platinum-iridium prototype electrode was used. Ventricular fibrillation was induced with a 60-Hz generator and allowed to continue for 10 seconds before a shock was given. Two different biphasic shock waveforms (3.2/2- and 6/6-millisecond) were delivered by the six electrode configurations. Eight dogs (weight, 24.5 +/- 1.3 kg) underwent an up-down defibrillation protocol. The order of testing the epicardial electrodes, the endocardial cathodes, and the waveform was randomized. With the epicardial carbon electrode, the mean defibrillation threshold (DFT) energy decreased 39% to 56% and the voltage decreased 24% to 35% compared with the titanium patch: from 8.3 +/- 2.5 to 4.9 +/- 3.6 J with the CPI lead and the 3.2/2-millisecond waveform, from 6.2 +/- 2.5 to 2.9 +/- 2.1 J with the carbon-platinum-iridium prototype, and from 6.4 +/- 3.4 J to 3.5 +/- 2.6 J with the Medtronic lead (P < or = .05). The DFT determinations with the 6/6-millisecond biphasic waveform showed a similar trend with slightly higher values.

CONCLUSIONS

Compared with a titanium patch, the new braided epicardial electrode significantly decreases the defibrillation energy requirements. This effect can be maximized by using an endocardial carbon-platinum-iridium prototype as cathode and a short duration biphasic waveform.

Sudden death in recipients of first-generation implantable cardioverter defibrillators: analysis of terminal events. Participating investigators

Clinical factors and terminal events associated with sudden death in 51 patients were analyzed from among a multicenter experience of 864 recipients of first generation automatic implantable cardioverter defibrillator (AICD) devices (single zone, committed, monophasic pulse with > or = 1 epicardial patch electrode) during the period May 1982-February 1988. For these 51 patients, mean age was 58 years and atherosclerotic heart disease was present in 84%, with a history of ventricular fibrillation (VF) in 61%, and inducible sustained ventricular tachycardia (VT) in 84%; mean left ventricular ejection fraction was 0.26. Nearly 80% experienced one or more appropriate AICD shocks during the median 9 month (range 0-46 months) period prior to death. Of 30 monitored deaths, the first documented terminal rhythm was VF in 12 (40%), VT in 8 (27%), and asystole or electromechanical dissociation in the remaining 10 (33%). Shocks were documented during terminal events in 21 (66%) of 32 witnessed cases of sudden death with activated devices. The proportion of monitored or witnessed sudden deaths that were known or presumed to be tachyarrhythmic (based on terminal VT, VF, or shocks) ranged from 69% (11/16 cases with activated/nondepleted devices and a defibrillation threshold [DFT] < or = 20 J) to 81% (29/36 cases on intention-to-treat basis). Of 27 patients with known or presumed sudden tachyarrhythmic death, the AICD had been deactivated prior to death in 4 (15%); activated, but depleted in 4 (15%); activated/nondepleted, but with DFT of 25 J in 4 (15%); and activated/nondepleted, but without DFT testing in 4 (15%). The remaining 11 (41%) known or presumed sudden tachyarrhythmic deaths occurred in patients with activated/nondepleted devices and DFT < or = 20 J; however, definite or suspected contributory factors (e.g., hematoma under epicardial patch, generator component failure, or drug-induced DFT rise) could be identified in 6 (55%) of 11 cases. Thus, in this first-generation AICD experience: 1) most sudden deaths occurred on the basis of a known or presumed tachyarrhythmia; and 2) an understanding of apparent "failure" of ICD therapy could often be gained through an integrated analysis of associated clinical factors and management practices, as well as device "hardware" function. These observations are likely to remain relevant, even with respect to newer generation ICDs.