Antiarrhythmic drug use in the implantable defibrillator arm of the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study

Background Previous retrospective or observational series suggest that many patients with an implantable cardioverter-defibrillator (ICD) will be trea ted with antiarrhythmic drugs (AADs) to modify the frequency or manifestati on of recurrent ventricular arrhythmias. The relative clinical benefit, how ever, is uncertain, and deleterious interactions can occur. The objective o f this clinical investigation was to study the need for, and effects of, co ncomitant AAD use with the ICD in a prospectively defined cohort. Methods All patients randomly assigned to the ICD arm of the Antiarrhythmic s Versus Implantable Defibrillators (AVID) study were followed for the addi tion of class I or III AADs ("crossover") after hospital discharge. Additio n of AADs was strictly regulated by AVID protocol. The timing and reasons f or crossover and the effects on ventricular arrhythmia recurrence were anal yzed. Patients were excluded if they required AADs before hospital discharg e after index arrhythmias or if they had no ventricular arrhythmia before i nitiation of AADs. Results After a median follow-up of 135 days, 81 (18%) of the 461 eligible patients required AADs and formed the crossover group. The primary reason f or crossover was frequent ICD shocks in 64% of patients. The most common AA D selected was amiodarone (in 42%). Independent predictors of crossover wer e lower ejection fraction, absence of ventricular fibrillation, or presence of nonsyncopal ventricular tachycardia at presentation, prior unexplained syncope, female sex, and history of cigarette smoking. Before AAD use, the 1-year arrhythmia event rate was 90%; after AAD, the event rate was only 64 % (P=.0001). The time to first event was extended from 3.9 +/- 0.7 months t o 11.2 +/- 1.8 months. There were 1.4 +/- 3.7 fewer ICD therapy events (P = .005) after crossover, predominantly accounted for by reduction in shocks r ather than anti-tachycardia pacing therapies. Conclusions The majority of patients who receive ICDs for sustained ventric ular tachycardia or ventricular fibrillation can be treated without AADs. M ost commonly, AADs are added to combat frequent ICD shocks, which are succe ssfully reduced by AAD therapy.