Prognostic Value of <scp>MRI</scp> ‐Based Left Ventricular Trabecular Complexity for Sudden Cardiac Death in Hypertrophic Cardiomyopathy

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a leading cause of sudden cardiac death (SCD). Early identification of high-risk patients is important for guiding preventive measures. PURPOSE: To validate left ventricular (LV) myocardial trabecular complexity using fractal dimension (FD) for SCD prediction in a larger cohort and investigate its relationship with sarcomere variants. STUDY TYPE: Prospective. POPULATION: 835 HCM patients (506 men; 50.7 ± 14.4 years). FIELD STRENGTH/SEQUENCE: Steady-state free precession (SSFP) cine sequence at 3 T. ASSESSMENT: Two cardiologists, blinded to clinical outcomes, independently analyzed assigned cardiac MRI cases. Biventricular function, late gadolinium enhancement, and LV FD were measured with fracAnalyse. The endpoint was SCD or aborted SCD. Sarcomere variants were classified by the American College of Medical Genetics and Genomics criteria, and their associations with FD were assessed. STATISTICAL TESTS: Cox regression assessed associations with SCD. Kaplan-Meier analysis and log-rank test were used to compare SCD incidence. Harrell's C-index assessed model discrimination. Welch's t-test compared FD between variant groups. Two-sided p < 0.05 indicated significance. RESULTS: Global FD (hazard ratio [HR] per 0.01 increase, 1.07, 95% CI: 1.01-1.15) and maximal apical FD (HR, 1.08, 95% CI: 1.02-1.14) independently predicted SCD after adjustment for European Society of Cardiology and American Heart Association risk predictors. High global FD (≥ 1.256) or maximal apical FD (≥ 1.352) improved model discrimination (C-index: 0.779-0.803, 0.77-0.791). MYBPC3 carriers had significantly higher maximal apical FD (1.35 ± 0.05 vs. 1.33 ± 0.07), maximal basal FD (1.35 ± 0.05 vs. 1.32 ± 0.06), and mean basal FD (1.28 ± 0.06 vs. 1.25 ± 0.07) than other sarcomere variant carriers. DATA CONCLUSION: LV global and apical FDs provide independent and incremental prognostic value for predicting SCD. MYBPC3 variant carriers exhibited elevated FD values, linking trabecular complexity with genetic variants in HCM. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 3.