RECENT CLINICAL EXPERIENCE WITH THE AUTOMATIC IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR.

The implantable defibrillator is a self-contained automatic diagnostic-therapeutic system, initially designed to recognize and treat ventricular fibrillation. More recently, a new generation of the device with additional cardioverting capabilities for treatment of sustained ventricular tachycardias was introduced into clinical practice. This automatic implantable cardioverter-defibrillator continuously monitors cardiac electrical activity, recognizes the presence of a life-threatening ventricular tachyarrhythmia, and then promptly delivers an electrical countershock to restore normal heart rhythm. If the discharge is ineffective, the device delivers a second and even a third and fourth countershock, after additional detection and charging periods lasting from 10 to 35 seconds; the energy of these additional pulses is increased to 30 joules. Thus, the complete four-pulse sequence may last up to 2 minutes or more. Higher-energy devices capable of delivering pulses of up to 40 or 45 joules are also available for patients in whom the defibrillating threshold is particularly high.