Temporal evolution of clinical event risk after primary-prevention ICD implantation: Chagas vs. non-Chagas dilated cardiomyopathy.

Chagas cardiomyopathy evolves through progressive myocardial injury that may alter the temporal distribution of arrhythmic risk compared with other dilated substrates. We analysed a two-centre registry of consecutive primary-prevention implantable cardioverter-defibrillator (ICD) recipients in Buenos Aires (2008-2025), excluding cardiomyopathies in which ICD indication is not based on ventricular dysfunction. The final cohort comprised 194 patients: 50 with Chagas cardiomyopathy (26%), 83 with ischaemic (43%) and 61 with non-ischaemic dilated cardiomyopathy (31%). Median LVEF was 30% in both groups. The primary endpoint was a composite of appropriate ICD therapy, adjudicated on stored electrograms, or all-cause death. Pre-planned analyses included multivariable Cox regression, period-specific models split at 5 years, competing-risk regression and restricted mean survival time (RMST). The endpoint occurred in 109 patients. Cumulative incidence was lower in Chagas patients at 1 year (2.1% vs. 12.2%) and 5 years (19.5% vs. 42.4%), and Chagas patients accumulated 682 additional event-free days at 10-year RMST (95% CI: 258-1047; p = 0.001). Chagas cardiomyopathy was associated with lower composite risk (hazard ratio 0.58; 95% CI: 0.37-0.91; p = 0.018), an association confined to the first 5 years (0.35; 0.17-0.75; p = 0.007) and no longer detectable thereafter (0.85; 0.47-1.54; p = 0.587), with 28 and 56 patients at risk at 5 years and 11 and 20 at 10 years. The wide confidence interval and small population at risk in the late period mean that absence of a detectable difference should not be read as evidence of equivalent risk. These findings are hypothesis-generating and require confirmation in larger cohorts.