Subendocardium-involved late gadolinium enhancement in non-ischemic dilated cardiomyopathy improves risk stratification of sudden cardiac death

AIMS: The prognostic value of late gadolinium enhancement (LGE) phenotypes-particularly subendocardial involvement-for sudden cardiac death (SCD) remains unclear in dilated cardiomyopathy (DCM). Whether LGE phenotype integrating pattern and location can improve SCD risk stratification is an unmet need. METHODS AND RESULTS: DCM patients who underwent cardiac MRI were retrospectively enrolled. The endpoint was a composite of SCD and surrogate SCD events. Among 902 patients (mean age 46 ± 14 years, 78.7% men), subendocardium-involved and mid-wall LGE were observed in 129 (14.3%) and 263 (29.1%) patients, predominantly involving the lateral (65.1%) and septal wall (97.7%), respectively. During a median follow-up of 77 months (IQR 40-92 months), 51 (5.7%) patients experienced SCD events. Multivariable analysis identified septal mid-wall LGE (HR 3.59; 95% CI 1.73-7.47; P = 0.001) and lateral subendocardium-involved LGE (HR 3.07; 95% CI 1.39-6.75; P = 0.005) as independent predictors. A three-tier risk stratification model was developed, classifying patients into: lowest risk (neither septal mid-wall nor lateral subendocardium-involved LGE; reference), intermediate risk (either phenotype alone; HR 4.8, 95% CI 2.2-10.46, P < 0.001), and highest risk (both phenotypes; HR 10.71, 95% CI 3.53-32.46, P < 0.001). The model showed the best improvement in model discrimination and reclassification over left ventricular ejection fraction (C-statistic improvement: 0.23; net reclassification improvement = 0.67; integrative discrimination index = 0.27; all P < 0.05). CONCLUSION: SCD was predicted by both lateral subendocardium-involved LGE and septal mid-wall LGE in DCM. The novel SCD risk model integrating these phenotypes demonstrated superior prognostic performance compared with conventional prognosticators.