Abstract
Indications for implantable cardioverter defibrillators (ICDs) are expanding. Defining long-term predictors of ICD therapies might help to identify those patients who will benefit most from implantation of an ICD. The objective of this study was to examine long-term predictors of appropriate ICD therapy among patients with coronary disease at high risk of sudden cardiac death.
An analysis of 245 patients with coronary disease, who had been implanted with an ICD for primary or secondary prevention of sudden cardiac death, was performed. Time to appropriate ICD therapy, defined as antitachycardia pacing or shock, was evaluated by the Kaplan-Meier method. Cox regression analysis was performed to determine hazard ratios for factors predicting appropriate ICD therapies.
During a mean (SD) follow-up of 41 (33) months, 115 patients (53%) experienced appropriate ICD therapy. Independent predictors of appropriate ICD therapy included advanced age, left ventricular ejection fraction (LVEF) < 35%, and impaired renal function, with covariate-adjusted hazard ratios of 1.36 per 10 years (95% CI, 1.11 - 1.66; P = 0.003), 1.78 (95% CI, 1.21 - 2.63; P = 0.004), and 1.59 (95% CI, 1.00 - 2.54; P = 0.050), respectively. Remote myocardial infarction (> 6 months prior to ICD implantation) was associated with higher probability of appropriate ICD therapy among patients with LVEF > 35% (adjusted HR 2.68 [95% CI, 1.05 - 6.86; P = 0.04]), but not among patients with LVEF < 35% (adjusted HR 1.09 [95% CI, 0.58 - 2.04; P = 0.79]).
Left ventricular ejection fraction, advanced age, and renal impairment are long-term predictors of appropriate ICD therapy in patients with coronary disease at high risk of sudden cardiac death. Patients with an ejection fraction above 35% have few arrhythmic events early after the myocardial infarction but appropriate therapies become more frequent late after the myocardial infarction, possibly due to progression of the disease.
