Abstract 13892: Fragmented QRS Activity Representing Inhomogeneous Left Ventricular Conduction on Magnetocardiography Predicts Adverse Outcomes in Patients With LBBB and Left Ventricular Dysfunction

Abstract

Background: Left bundle branch block (LBBB) is known to be a risk factor in patients with heart failure or structural heart diseases. We have already reported that the fragmented QRS (fQRS) activity on QRS vector magnitude waveform (VMW) derived from high-resolution multi-channel magnetocardiography (MCG) represents heterogeneous left ventricular (LV) activation sequences due to myocardial scar and can predict adverse outcomes in patients with dilated and hypertrophic cardiomyopathy. Therefore, we investigated whether MCG also can predict the outcome of patients with LBBB noninvasively using fQRS. Methods: 64-ch MCG was recorded in 58 patients with LV dysfunction (LVEF<45%) and LBBB (QRS interval ≥120ms). Clinical characteristics, electrocardiographic parameters, and clinical outcomes were compared between patients with and without fQRS on the QRS VMW, which was constructed from 64 superimposed signals during sinus rhythm. The fQRS on MCG was defined as the presence of ≥1 discrete component larger than 20% of the maximum amplitude within QRS complex. Results: The fQRS was identified on MCG in 29 patients (Group-A), but not in the rest of 29 patients (Group-B). Age, Sex, presence of structural heart disease, QRS or QTc interval, fQRS (≥8 spikes in leads I, aVL, V5 and V6) on 12-lead ECG, history of arrhythmias, LVEF, and medications were not different between 2 groups. During the follow-up of 30 ± 23 months, cardiac events (sudden cardiac death, heart failure, hospitalization, and life-threatening arrhythmia) occurred more frequently in the Group-A (17/29, 58.6%) than in the Group-B (3/29, 10.3%; p < 0.0002), although patients with fQRS on ECG showed the similar event rate to those without. Multivariate analysis revealed that the presence of fQRS on MCG was only an independent predictor of poor outcome (p=0.0137). Conclusions: The prognosis of LBBB patients with fQRS on MCG was poor. The fQRS on MCG, which indicates the presence of inhomogeneous LV conduction, can be a reliable marker for predicting adverse outcomes in patients not only with cardiomyopathy but also with LBBB.