Scar Architecture as a Structural Biomarker of Ventricular Arrhythmias and Sudden Cardiac Death in Patients with Hypertrophic Cardiomyopathy: a Cardiac Magnetic Resonance Study

Background: Myocardial scarring assessed by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) predicts sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). Post-processing enables characterization of scar components: borderzone (BZ), core, and BZ channels. Objective and methods: Evaluate scar composition as a predictor of VT/VF beyond traditional risk factors in HCM. We retrospectively analyzed HCM patients who underwent LGE-CMR. Scar components, alone or combined with ESC or ACC/AHA risk scores, were tested as predictors of a composite VT/VF endpoint (SCD, sustained VT, ICD therapy, or cardiac arrest). Results: Four-hundred-ten patients (67% males, 55 years IQR:41-65) were included, 298 of whom (72.6%) had LGE at CMR (LGE+). Total scar, BZ and core mass were 7.3% (IQR:0.0-14.3), 6.4% (IQR:0.0-12.2), and 0.9% (IQR:0.0-2.1) of LV mass, respectively. BZ channels were found in 140 (34.1%) patients. At follow-up (65 months;IQR:36-95), 26 (6.3%) patients met the endpoint. Total scar, BZ and core mass were higher in VT/VF patients (p<0.001). BZ channels were observed in 88.5% of VT/VF patients vs 30.5% of those without (p<0.001). Patients with BZ channels had higher incidence of VT/VF. BZ channels mass was associated with an increased risk of VT/VF after adjustment for ESC (HR:1.45; 95%CI:1.26-1.67; p< 0.0001) and AHA/ACC (HR:1.34; 95%CI:1.16-1.54; p< 0.0001) risk estimate. The predictive performance of both ESC and AHA/ACC models was enhanced by integrating BZ channel mass (NRI:0.19, p=0.03 and 0.32, p<0.001, respectively). Conclusions: Scar composition and its organization in BZ channels provides strong, independent prognostic value for VT/VF in HCM, improving existing clinical risk stratification tools.