Significant advances in the basic science of implantable cardioverter-
defibrillator therapy have led to improvements in defibrillation wavef
orms and in capacitor technology. Nonthoracotomy devices with biphasic
waveforms can be implanted with a near 100% success rate. Although fe
wer patients with implantable cardioverter-defibrillators are being tr
eated with concomitant antiarrhythmic drug therapy, sotalol appears to
decrease the defibrillation threshold. Controversy still exists over
the optimal design for defibrillator sensing leads. Tachyarrhythmia de
tection enhancements increase specificity for sensing ventricular tach
ycardia but may risk undersensing. A variety of subsets of patients re
ceiving implantable cardioverter-defibrillators have been identified;
patients presenting with ventricular fibrillation appear to have the m
ost unfavorable prognosis. Controversy exists as to the true impact of
implantable cardioverter-defibrillator therapy on subsequent survival
. Randomized clinical trials such as AVID (Antiarrhythmics Versus Impl
antable Defibrillators) are designed to determine the true benefits of
implantable cardioverter-defibrillators and may lead to expanded indi
cations.