Impact of ICD and CRT-D implantation on survival in ischemic and non-ischemic cardiomyopathy: a single-center croatian retrospective cohort study and comparative insights with the DANISH trial

Abstract Background Implantable cardioverter-defibrillators (ICDs) reduce sudden cardiac death (SCD) in heart failure (HF) patients, especially in those with ischemic cardiomyopathy (ICM). However, the overall impact on mortality in non-ischemic cardiomyopathy (NICM) is still debated. The DANISH trial raised questions about ICD efficacy in NICM patients, particularly in older individuals, sparking concerns regarding patient selection and the risk-benefit balance. This study evaluates survival outcomes, device activation, and mortality predictors in ICM and NICM patients with implanted ICD devices. Methods A total of 786 patients who underwent ICD (75%) or CRT-D (25%) implantation between 2009 and 2018 were included in this retrospective cohort study. The mean patient age was 58.2 ± 13.6 years, with 80.7% being male and a reduced left ventricular ejection fraction (LVEF) of 31.9 ± 12.4%. The primary outcome was all-cause mortality, and secondary outcomes included device activation (appropriate or inappropriate) and its correlation with survival. Kaplan-Meier survival estimates and Cox proportional hazard models were used, with comparisons between ischemic and non-ischemic cardiomyopathy patients and primary versus secondary prevention groups. Results Over follow-up period of +/-47.3 months, 35.2% died. Device activation occurred in 29.1% of patients, with 86% being appropriate. ICM patients had a higher rate of appropriate activations compared to NICM patients (28.0% vs. 23.0%), while inappropriate activations were more frequent in NICM patients (6.1% vs. 1.5%, p=0.003). Device activation was associated with a significant survival advantage (p<0.001). Mortality predictors included older age, non-sustained ventricular tachycardia (NSVT), and a history of decompensation. Cox regression analysis confirmed these as independent mortality predictors, with hazard ratios of age (HR=1.032; p<0.001), NSVT (HR=2.403; p<0.001), and decompensation (HR=1.931; p<0.001). In comparison with the DANISH trial, which reported no significant reduction in all-cause mortality in NICM patients over 70 years old, this study found similar age-dependent survival benefits. Younger patients (<70 years), (especialy with NICM), showed greater survival benefits from ICD implantation. Results emphasize the importance of careful patient selection, especially in older patients, where the benefits of ICDs must be balanced against the risks of inappropriate shocks and device complications. Conclusion This study found that ICD implantation improved survival. Age, NSVT, and decompensation were key predictors of mortality and device activation, highlighting the need for individualized patient assessments. In line with the DANISH trial, our findings suggest that younger NICM patients benefit more from ICD implantation, while in older populations, the risks and benefits should be carefully weighed.