BACKGROUND: Better risk stratification is needed to evaluate patients with nonischemic cardiomyopathy (NICM) for prophylactic implantable cardioverter-defibrillators (ICDs). Growing evidence suggests that cardiac magnetic resonance (CMR) imaging may be useful in this regard. OBJECTIVE: We aimed to determine if late gadolinium enhancement (LGE) seen on CMR (dichotomized as none or minimal <
2% vs significant ≥2%) predicts appropriate ICD therapies (primary endpoint) or all-cause mortality/transplant/left-ventricular assist device (LVAD) implantation (secondary endpoint) in patients with NICM. METHODS: We identified 344 patients with NICM who underwent primary prevention ICD implantation at Cleveland Clinic between 2003 and 2021 with CMR within 12 months before implant. LGE was calculated as percentage myocardium with pixel intensity ≥5 standard deviations higher than that of reference myocardium. Endpoints were adjudicated retrospectively by chart review. RESULTS: A total of 125 of 344 patients (36%) had none or minimal LGE, and 219 (64%) had significant LGE. Over a median follow-up of 61 months, 53 patients (24%) with significant LGE vs 10 (8%) with none or minimal LGE met the primary endpoint, and 56 patients (26%) vs 21 (17%) met the secondary endpoint, respectively. Significant LGE predicted the primary outcome in multivariable competing-risks regression (hazard ratio [HR] 2.99, 95% confidence interval [CI] 1.48-6.02, P = .002), but did not predict the secondary outcome in multivariable Cox regression (HR 1.34, 95% CI 0.78-2.29, P = .287). CONCLUSION: In patients with NICM and primary prevention ICDs, LGE ≥2% is predictive of appropriate device therapies but not all-cause mortality/LVAD/transplant. LGE may be a relatively specific predictor of sudden cardiac arrest risk and therefore could potentially be used during evaluation for prophylactic ICD implantation.