Comparison of Mortality and Readmission in Non-Ischemic Versus Ischemic Cardiomyopathy After Implantable Cardioverter-Defibrillator Implantation.

Data is lacking on the contemporary risk of death and readmission following implantable cardioverter-defibrillator (ICD) implantation in patients with non-ischemic cardiomyopathies (NICM) compared with ischemic cardiomyopathies (ICM) in a large nationally representative cohort. We performed a retrospective cohort study using the National Cardiovascular Data Registry ICD Registry linked with Medicare claims from April 1, 2010 to December 31, 2013. We established a cohort of NICM and ICM patients with a left ventricular ejection fraction ≤35% who received a de novo, primary prevention ICD. We compared mortality and readmission using Kaplan-Meier curves and Cox proportional hazard regressions models. We also evaluated temporal trends in mortality. In 31,044 NICM and 68,458 ICM patients with a median follow up of 2.4 years, 1-year mortality was significantly higher in ICM patients (12.3%) compared with NICM (7.9%, p < 0.001). The higher mortality in ICM patients remained significant after adjustment for covariates (hazard ratio [HR] 1.40; 95% confidence interval [CI] 1.36 to 1.45), and was consistent in subgroup analyses. These findings were consistent across the duration of the study. ICM patients were also significantly more likely to be readmitted for all causes (adjusted HR 1.15, CI 1.12 to 1.18) and for heart failure (adjusted HR 1.25, CI 1.21 to 1.31). In conclusion, the risks of mortality and hospital readmission after primary prevention ICD implantation were significantly higher in patients with ICM compared with NICM which was consistent across all patient subgroups tested and over the duration of the study.