Study Objective: To assess the efficacy of the automatic implantable cardioverter-defibrillator in preventing sudden death in high-risk patients.
Design: Nonrandomized cohort study.
Setting: A university teaching hospital with 500 beds.
Patients: Consecutive sample of 78 patients with symptomatic, sustained ventricular tachyarrhythmias that were previously drug-refractory.
Interventions: Before February 1985, patients received treatment with the defibrillator and amiodarone if they presented with loss of consciousness (group A) and amiodarone alone if they did not lose consciousness (group C). After February 1985, because the availability of the defibrillator was severely curtailed, patients who lost consciousness received treatment with amiodarone alone (group B).
Measurements and Main Results: The risk for recurrent arrhythmias was similar between groups. The actuarial risk for sudden death in group B was 31% (95% confidence interval, 11% to 51%) at 1 and 2 years, a value that was significantly higher than that for group A (p < 0.003) or group C (p < 0.03). The risk for dying suddenly with the first recurrence was 0.78 in group B, a value that was significantly higher than that for group A (p < 0.003) or group C (p < 0.002).
Conclusion: The defibrillator is highly effective in preventing sudden death in patients whose presenting arrhythmias caused loss of consciousness (group A). In patients whose presenting arrhythmias did not result in loss of consciousness (group C), initial treatment with the defibrillator appears unnecessary.