Aims: Primary prevention implantable cardioverter defibrillator (ICD) is not generally recommended in New York Heart Association (NYHA) I class patients with dilated cardiomyopathy (DCM). This study sought to assess the competing risk of sudden cardiac death (SCD) in DCM patients with left ventricular ejection fraction (EF) ≤35% and NYHA I class. Methods: A total of 272 DCM patients with EF ≤35% and NYHA class I–III after ≥3 months of guideline-directed medical therapy were included. The risk of SCD and SCD/malignant ventricular arrhythmias (MVA) was assessed in NYHA I vs. NYHA II and NYHA III groups by competing risk analysis. Results: NYHA I patients were younger, had higher EF and smaller left atrium, were less likely receiving mineral corticoid receptor antagonists. The cumulative incidence of SCD (p = 0.92) and SCD/MVA (p = 0.42) did not differ between NYHA I vs NYHA II–III classes. NYHA class did not influence the association between ICD and SCD risk (p for interaction = 0.125). Conclusions: In this cohort of DCMs, patients with EF ≤35% and NYHA I class were exposed to a risk of SCD and life-threatening arrhythmias not different from NYHA II–III. Therefore, inclusion of asymptomatic patients with DCM and systolic dysfunction should be strongly considered in future randomized studies on primary prevention ICD.
