Sudden death in recipients of transvenous implantable cardioverter defibrillator systems: Terminal events, predictors, and potential mechanisms

Sudden Death in ICD Recipients. Introduction: Transvenous implantable cardi overter defibrillator (ICD) systems are very effective in preventing sudden death; however, little is known about terminal events and potential causes and mechanisms of sudden death in recipients of these devices. Methods and Results: We analyzed 74 cases of sudden death among patients en rolled in several clinical investigations of transvenous ICD systems. Eight y-one percent were men (mean age 68 +/- 10 years), 86% had coronary artery disease, mean left ventricular ejection fraction was 0.27 +/- 0.11, and two thirds presented with sustained ventricular tachycardia. The final event w as witnessed in 65 patients (81%). Based on reported ICD shocks, documented rhythm, and/or postmortem device data, sudden death was deemed tachyarrhyt hmic in 49 cases (66%), non-tachyarrhythmic in 12 (16%), and indeterminate in the remaining 13 (18%). Multivariate analysis of several clinical and no nclinical factors found advanced age (> 65 years, P = 0.03, odds ratio [OR] 1.75, 95% confidence interval [CI] 1.05 to 2.92), reduced left ventricular ejection fraction (< 0.35, P < 0.01, OR 3.51, CI 1.66 to 7.40), and having antibradycardia pacing ICDs (P = 0.02, OR 5.26, CI 1.37 to 20.0) to be ind ependent predictors of sudden death. One or more predisposing factors and/o r potential causes of sudden death were identified in 21 patients (28%), Conclusion: In this select group of transvenous ICD recipients, (1) sudden death was associated with ventricular tachycardia/ventricular fibrillation in at least two thirds of cases, (2) nearly one third of patients had one o r more factors, some device related, that could have been associated with s udden death, and (3) death ensued despite appropriate ICD therapies and, in many cases, external resuscitation, suggesting acute adverse events as com mon terminal factors.