H eart failure affects 1 million to 2 million adults in the United States alone. 1 In the majority of patients, an inexorable, although often slow, deterioration of ventricular function occurs, and only 60% survive 4 years. 2 Although the long-term outcome is viewed with pessimism, death is classified as sudden and" unexpected" in up to 80% of patients. One may ask whether any death preceded by months or years of chronic heart failure can truly be called sudden. Sudden death is often defined as death preceded by a short duration, typically< 1 hour, of acute symptoms. 3, 4 In the adult United States population, ventricular fibrillation in the setting of coronary artery disease is the most common scenario identifiedby this definition. Many heart failure patients periodically suffer mild exacerbations of heart failure that require adjustment of their medical regimen but have good functional status between exacerbations. In such circumstances, out-ofhospital ventricular fibrillation during a mild heart failure exacerbation may not meet everyone's definition of sudden death. Even if one focuses on" arrhythmic death," the clinical implications are not alwaysstraightforward. Preventing ventricular fibrillation in a patient with mild dyspnea on climbing hills is clearly desirable. Preventing ventricular fibrillation in a patient with no option for cardiac transplantation who is bedridden with resting dyspneadespite maximal medical therapy may not be an appropriate therapeutic goal. From a clinically practical standpoint, suddendeath could be considered an unexpected deaththat occurs without sufficient warning to allow an ambulatory patient to seek medical assistance before the fatal collapse.

Is Sudden Death Prevention Desirable When Ventricular Dysfunction Is Advanced? The risk of sudden death increases with the severity of heart failure. 5-9 In patients who are referred for possible cardiac transplantation, an increased risk of sudden death has been associated with lower left ven-tricular ejection fraction, elevated pulmonary capillary wedge or pulmonary artery pressures, and hyponatremia. When sudden death is produced by a reversible arrhythmia that is not the last gasp of an end-stage ventricle, then prevention of sudden death mayprolong