Abstract
BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) face an increased risk of sudden cardiac death (SCD), and myocardial fibrosis is predictive of ventricular arrhythmias. OBJECTIVE: This study aimed to determine whether the location, pattern, and quantification of myocardial fibrosis predict SCD in patients with HCM after cardiac implantable electronic device (CIED) implantation. METHODS: This study included patients with HCM who completed cardiovascular magnetic resonance and received CIED between June 2017 and January 2023. The primary outcome was SCD or SCD-equivalent events (composite of SCD, resuscitated cardiac arrest, sustained ventricular tachycardia or ventricular fibrillation, or appropriate implantable cardioverter-defibrillator therapy). RESULTS: 88 patients were included (age 52.3 ± 15.3 years; 67.0% male). Over a median follow-up period of 38.1 months, 27 SCD events (30.6%) were recorded. Fibrosis in the inferior wall, transmural pattern, total fibrosis, and gray zone fibrosis (GZF) were all significantly associated with SCD risk. Stepwise regression analyses identified the transmural fibrosis pattern (hazard ratio 3.15; 95% confidence interval [CI] 1.22-8.14; P = .018) and increased GZF(6SD) (hazard ratio 3.49; 95% CI 1.31-9.25; P = .012) as independent predictors of SCD risk. Incorporating both transmural fibrosis and GZF(6SD) of ≥21.00% into the HCM 5-year SCD risk model significantly improved predictive value from 0.69 (95% CI 0.54-0.84) to 0.76 (95% CI 0.62-0.89; P for comparison = .002). The net reclassification improvement was 0.35 (95% CI 0.13-0.57; P = .002), and the integrated discrimination improvement was 0.04 (95% CI 0.02-0.06; P < .001). CONCLUSION: Transmural fibrosis and elevated GZF(6SD) are predictors of SCD in patients with HCM after CIED implantation and provide additional value to the existing risk scoring system.