Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy.

Background: Hypertrophic cardiomyopathy is a genetic disease associated wit h a risk of ventricular tachyarrhythmias and sudden death, especially in yo ung patients. Methods: We conducted a retrospective multicenter study of the efficacy of implantable cardioverter-defibrillators in preventing sudden death in 128 p atients with hypertrophic cardiomyopathy who were judged to be at high risk for sudden death. Results: At the time of the implantation of the defibrillator, the patients were 8 to 82 years old (mean [+/-SD], 40+/-16), and 69 patients (54 percen t) were less than 41 years old. The average follow-up period was 3.1 years. Defibrillators were activated appropriately in 29 patients (23 percent), b y providing defibrillation shocks or antitachycardia pacing, with the resto ration of sinus rhythm; the average age at the time of the intervention was 41 years. The rate of appropriate defibrillator discharge was 7 percent pe r year. A total of 32 patients (25 percent) had episodes of inappropriate d ischarges. In the group of 43 patients who received defibrillators for seco ndary prevention (after cardiac arrest or sustained ventricular tachycardia ), the devices were activated appropriately in 19 patients (11 percent per year). Of 85 patients who had prophylactic implants because of risk factors (i.e., for primary prevention), 10 had appropriate interventions (5 percen t per year). The interval between implantation and the first appropriate di scharge was highly variable but was substantially prolonged (four to nine y ears) in six patients. In all 21 patients with stored electrographic data a nd appropriate interventions, the interventions were triggered by ventricul ar tachycardia or fibrillation. Conclusions: Ventricular tachycardia or fibrillation appears to be the prin cipal mechanism of sudden death in patients with hypertrophic cardiomyopath y. In high-risk patients with hypertrophic cardiomyopathy, implantable defi brillators are highly effective in terminating such arrhythmias, indicating that these devices have a role in the primary and secondary prevention of sudden death. (N Engl J Med 2000;342:365-73.) (C)2000, Massachusetts Medica l Society.