Clinical risk stratification for primary prevention implantable cardioverter defibrillators

Background — A conceptualized model may be useful for understanding risk stratification of primary prevention implantable cardioverter defibrillators (ICDs) considering the competing risks of appropriate ICD shock vs mortality.

Methods and Results — In a prospective, multicenter, population-based cohort with left ventricular ejection fraction (LVEF) ≤35% referred for primary prevention ICD, we developed dual risk stratification models to determine the competing risks of appropriate defibrillator shock versus mortality using a Fine-Gray subdistribution hazard model. Among 7020 patients referred, 3445 underwent defibrillator implant (79.7% men, median 66 years [25^th, 75^th: 58-73]). During 5918 person-years of follow-up, appropriate shock occurred in 204 patients (3.6 shocks/100 person-years) and 292 died (4.9 deaths/100 person-years). Competing risk predictors of appropriate shock included nonsustained ventricular tachycardia, atrial fibrillation, serum creatinine concentration, digoxin or amiodarone use, and QRS duration near 130-millisecond peak. One-year cumulative incidence of appropriate shock was 0.9% in the lowest-risk category, and 1.7%, 2.5%, 4.9%, and 9.3% in low, intermediate, high, and highest-risk groups, respectively. Hazard ratios for appropriate shock ranged from 4.04 to 7.79 in the highest three deciles (all p ≤.001 vs lowest-risk). Cumulative incidence of one-year death was 0.6%, 1.9%, 3.3%, 6.2%, and 17.7% in lowest, low, intermediate, high, and highest-risk groups, respectively. Mortality hazard ratios ranged from 11.48 to 36.22 in the highest three deciles (all p <.001 vs lowest-risk).

Conclusions — Simultaneous estimation of risks of appropriate shock and mortality can be performed using clinical variables, providing a potential framework for identification of patients who are unlikely to benefit from prophylactic ICD.