Intermittent Left Bundle Branch Block After Transcatheter Aortic Valve Replacement: Electrophysiological and Clinical Significance.

CASE SUMMARY: An 87-year-old man with pre-existing first-degree atrioventricular block underwent transfemoral transcatheter aortic valve replacement (TAVR) for severe aortic stenosis. Postprocedure, he developed worsening first-degree atrioventricular block and intermittent left bundle branch block with a paradoxical electrocardiographic pattern: Slightly longer PR intervals were associated with narrow QRS beats, whereas shorter PR intervals resulted in marked QRS widening. Electrophysiology study revealed advanced infra-Hisian conduction disease, with greater prolongation of the His-ventricular interval before narrow QRS beats, prompting permanent pacemaker implantation.

TAKE-HOME MESSAGE: This case demonstrates that intermittent left bundle branch block after TAVR-particularly when associated with marked PR prolongation preceding apparent QRS narrowing-warrants careful evaluation, as it may mask high-risk trifascicular disease.