Implantable cardioverter-defibrillators: a new preventive medical option

Implantable cardioverter-defibrillator (ICD or defibrillator) therapy has revolutionized the fields of cardiology and electrophysiology. Hundreds of thousands of patients at risk for sudden cardiac death receive them each year. The devices are not much larger than a pacemaker, and they have full pacemaker capabilities in addition to being able to shock patients out of life-threatening ventricular arrhythmias. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) in 1996 was a landmark trial that showed for the first time a mortality benefit of ICD therapy over medications in patients at high risk for sudden death. Multicenter Automatic Defibrillator Implantation Trial II, published in 2002, extended these results to all patients with ischemic heart failure with depressed heart function. Candidates for ICD implantation include most patients with an ejection fraction of <30%, especially those with coronary artery disease. More work needs to be done to define those patients with nonischemic cardiomyopathies who will benefit from ICDs and biventricular pacing for heart failure.