Myocardial fibrosis predicts sudden cardiac death in patients with hypertrophic cardiomyopathy after cardiac electronic device implantation: Insights from cardiovascular magnetic resonance imaging.

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 GZF6SD (hazard ratio 3.49; 95% CI 1.31-9.25; P = .012) as independent predictors of SCD risk. Incorporating both transmural fibrosis and GZF6SD 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 GZF6SD are predictors of SCD in patients with HCM after CIED implantation and provide additional value to the existing risk scoring system.