Impact of the presence and amount of myocardial fibrosis by cardiac magnetic resonance on arrhythmic outcome and sudden cardiac death in nonischemic dilated cardiomyopathy.

Background: Current risk stratification for sudden cardiac death (SCD) in nonischemic dilated cardiomyopathy (NIDC) relies on left ventricular (LV) dysfunction, a poor marker of ventricular electrical instability. Contrast-enhanced cardiac magnetic resonance has the ability to accurately identify and quantify ventricular myocardial fibrosis (late gadolinium enhancement [LGE]).

Objective: To evaluate the impact of the presence and amount of myocardial fibrosis on arrhythmogenic risk prediction in NIDC.

Methods: One hundred thirty-seven consecutive patients with angiographically proven NIDC were enrolled for this study. All patients were followed up for a combined arrhythmic end point including sustained ventricular tachycardia (VT), appropriate implantable cardioverter-defibrillator (ICD) intervention, ventricular fibrillation (VF), and SCD.

Results: LV-LGE was identified in 76 (55.5%) patients. During a median follow-up of 3 years, the combined arrhythmic end point occurred in 22 (16.1%) patients: 8 (5.8%) sustained VT, 9 (6.6%) appropriate ICD intervention, either against VF (n = 5; 3.6%) or VT (n = 4; 2.9%), 3 (2.2%) aborted SCD, and 2 (1.5%) died suddenly. Kaplan-Meier analysis revealed a significant correlation between the LV-LGE presence (not the amount and distribution) and malignant arrhythmic events (P < .001). In univariate Cox regression analysis, LV-LGE (hazard ratio [HR] 4.17; 95% confidence interval [CI] 1.56-11.2; P = .005) and left bundle branch block (HR 2.43; 95% CI 1.01-5.41; P = .048) were found to be associated with arrhythmias. In multivariable analysis, the presence of LGE was the only independent predictor of arrhythmias (HR 3.8; 95% CI 1.3-10.4; P = .01).

Conclusions: LV-LGE is a powerful and independent predictor of malignant arrhythmic prognosis, while its amount and distribution do not provide additional prognostic value. Contrast-enhanced cardiac magnetic resonance may contribute to identify candidates for ICD therapy not fulfilling the current criteria based on left ventricular ejection fraction.