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

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.