Although major advances have been made in the prevention, diagnosis, and treatment of cardiovascular diseases, the prevalence of these diseases in the US population is almost 62 million, with almost 8 million having had a myocardial infarction and nearly 5 million with a diagnosis of heart failure. Increasingly implantable devices have been used to decrease mortality and morbidity in patients with coronary heart disease. The dramatic reduction in mortality reported in the recent clinical trial of implantable cardioverter defibrillators in MADIT II (Multicenter Automatic Defibrillator Trial II) and decrease in hospitalizations, improved exercise tolerance, and better quality of life with cardiovascular resynchronization therapy reported in MIRACLE (Multicenter InSync Randomized Clinical Evaluation) led the American Heart Association to name treatment with implantable devices as one of the top 10 research advances for 2002. This article reviews the pathophysiology of cardiac dysrhythmia in the context of either heart failure or low ejection fraction, standard medical therapy, results of important clinical trials of implantable cardioverter-defibrillator and offers suggestions for future directions.