Clinical Trials of Implantable Defibrillators

Implantable cardioverter–defibrillators met with much uncertainty when first applied in clinical practice, as zealots and skeptics debated their value. Two points in their favor were clear from the beginning: the technology worked once energy sources and lead development were mastered, and such “safety net” therapy is rational, given the frequency and unpredictability of fatal arrhythmias. However, there were several countervailing sources of concern. These devices cannot help the 20 to 30 percent (or more) of patients with cardiac arrests caused by bradyarrhythmias or asystole.1 Furthermore, the majority of cardiac arrests occur in patients with cardiac diseases that are chronic and . . .