Mortality Benefit of Implantable Cardioverter-Defibrillator Therapy in Patients With Persistent Malignant Ventricular Arrhythmias Despite Amiodarone Treatment

Abstract

Implantable cardioverter defibrillators (ICDs) are very effective in preventing sudden cardiac death. However, debate continues as to whether ICD implantation is superior to amiodarone in prolonging survival in patients with life-threatening ventricular arrhythmias. Of 442 consecutive patients treated with amiodarone, we identified 48 patients with symptomatic ventricular arrhythmias who met all of the following inclusion criteria: (1) had inducible sustained ventricular tachycardia at baseline electrophysiologic study, (2) had an oral amiodarone load of at least 10 g over 10 to 14 days, (3) remained inducible with a hemodynamically unstable ventricular arrhythmia at follow-up electrophysiologic study, and (4) were advised to continue amiodarone therapy and undergo ICD implantation. Patients who agreed to undergo ICD implantation (n = 28) had a lower ejection fraction (29 ± 9% vs 40 ± 12% p <0.005) and were younger (61.0 ± 10 vs 69 ± 7 years, p <0.01) than patients who refused device implantation (n = 20). Using a Cox proportional-hazards model, defibrillator therapy was the strongest independent predictor of improved survival in patients with an ejection fraction ≤40% (RR = 0.42; 95% confidence interval 0.22 to 0.79). Thus, patients with depressed ejection fraction and continued inducibility of sustained ventricular tachycardia despite oral amiodarone loading have a poor prognosis. In such patients, ICDs are associated with a 58% reduction in total cardiac mortality. The purpose of the present study was to determine whether implantable cardioverter-defibrillator (ICD) therapy is associated with prolongation of total cardiac survival in patients with symptomatic ventricular arrhythmias refractory to amiodarone treatment. We found that ICD treatment was the strongest independent predictor of improved survival and was associated with a 58% reduction in cardiovascular mortality in patients with an ejection fraction ≤40% (RR 0.42; 95% confidence interval 0.22 to 0.79).