Magnetic Resonance Imaging Correlates of Left Bundle Branch Disease in Patients With Nonischemic Cardiomyopathy

Twelve-lead electrocardiogram and cardiovascular magnetic resonance were performed in 196 consecutive patients with NIC. The presence and extent of myocardial fibrosis was evaluated with late gadolinium enhancement (LGE) technique. Compared with normal intraventricular conduction patients, those with LBD were older (66 vs 59 years, p = 0.001), had greater LV volumes (p = 0.035 for end-diastolic and p = 0.009 for end-systolic volume) and mass (p = 0.034), and showed lower LV ejection fraction (33% vs 40%, p = 0.008). LGE was observed more commonly in LBD than in normal intraventricular conduction patients and was more often located in the ventricular septum (p < 0.001). On multivariate analysis, septal LGE was independently associated with a higher likelihood of LBD (odds ratio 6.1, 95% confidence interval 2.9 to 12.7, p < 0.001), even after correction for LV volumes, mass, and ejection fraction. In conclusion, in NIC, the presence of LBD is associated with worse LV remodeling and dysfunction than normal intraventricular conduction. Septal fibrosis yielded a 6-fold greater likelihood of LBD, independently of the degree of LV dilatation and systolic dysfunction.