IntroductionCardiac magnetic resonance (CMR)-identified late gadolinium enhancement (LGE), representing regional fibrosis, is often used to predict ventricular arrhythmia risk in nonischemic cardiomyopathy (NICM). However, LGE is more closely correlated with sustained monomorphic ventricular tachycardia (SMVT) than ventricular fibrillation (VF). We characterized CMR findings of ventricular LGE in VF survivors.MethodsWe examined consecutively resuscitated VF survivors undergoing contrast-enhanced 1.5T CMR between 9/2007 and 7/2016. We excluded coronary artery disease, hypertrophic cardiomyopathy, amyloid, sarcoid, arrhythmogenic right ventricular cardiomyopathy, and channelopathy. Preexisting implantable cardioverter-defibrillator (ICD) was a CMR contraindication. VF patients were divided into three groups: (1) NICM, (2) left ventricular (LV) dilatation with normal LV ejection fraction (LVEF), and (3) normal LV size and LVEF. Two groups of NICM patients with and without SMVT were examined for comparison.ResultsWe analyzed 87VF patients, and found that LGE was seen in 8/22 (36%) with NICM (LVEF 3811%, LV end-diastolic volume index [LVEDVI] 134 +/- 68mL/BSA), 11/40 (28%) with LV dilatation and normal LVEF (LVEDVI 103 +/- 17mL/BSA), 4/25 (16%) with normal LV size and LVEF. Incidence of LGE in NICM patients without prior ventricular tachycardia/VF (LVEF 36 +/- 12%, LVEDVI 141 +/- 46mL/body surface area [BSA]) was 117/277 and was not lower than those with VF and NICM (42%vs 36%; P=0.59). By contrast, 22/37 NICM patients with SMVT (LVEF 42 +/- 11%, LVEDVI 123 +/- 48mL/BSA) were LGE-positive (59% NICM-SMVT vs 36% NICM-VF; P=0.04).ConclusionMost VF survivors with a diagnosis of NICM did not have LGE on CMR and would not have met primary prevention ICD criteria based on LVEF. Absence of LGE may not portend a benign prognosis in NICM. Novel strategies for determining SCD risk in this cohort are required.