Prevalence and clinical significance of masquerading bundle branch block in patients undergoing transcatheter aortic valve replacement: Insights from a single-center registry

Abstract

Background: Masquerading bundle branch block (MBBB) is a rare electrocardiographic (ECG) pattern combining features of left bundle branch block and right bundle branch block (RBBB), reflecting advanced conduction disease. Given the high pacemaker implantation rate post-transcatheter aortic valve replacement (TAVR), preprocedural recognition of MBBB may hold clinical relevance.

Objective: This study aimed to assess the prevalence and clinical impact of MBBB in TAVR patients.

Methods: Consecutive TAVR cases (2010-2023) from a single-center database were reviewed. Pre-TAVR ECGs were classified by bundle branch block subtype by 2 blinded cardiologists, with discrepancies resolved by arbitration. Pacemaker implantation within 30 days was assessed.

Results: Of 1085 patients, 980 were included after excluding 72 with preexisting devices, 15 owing to missing data, 2 with pre-excitation, and 16 in-hospital deaths. Conduction abnormalities included MBBB in 13 (1.3%), RBBB in 151 (15.4%), and left bundle branch block in 158 (16.1%). All MBBB cases were initially mislabeled as RBBB, representing 7.9% of that group. Early pacemaker implantation was required in 166 patients (16.9%), including 92.5% of MBBB cases and 44.3% of RBBB cases. At 1 year after TAVR, 38% of patients with MBBB had died or were hospitalized for heart failure.

Conclusion: MBBB is not rare in TAVR candidates, occurring in approximately 8% of pre-TAVR ECGs labeled as RBBB. Its potential association with early pacemaker implantation highlights the need for careful preprocedural identification.

Keywords: Electrocardiography; Masquerading bundle branch block; Pacemaker implantation; Right bundle branch block; Transcatheter aortic valve replacement.