Phase 4 Atrioventricular Block Following Transcatheter Aortic Valve Replacement: Unmasking Latent Conduction Disease

Transcatheter aortic valve replacement (TAVR) carries up to a 15% risk of complete heart block (CHB) within 30 days, but the mechanisms driving recurrent heart block after the apparent initial conduction system recovery post-TAVR remain incompletely understood. Phase 4 atrioventricular block, a pause-dependent phenomenon occurring when supraventricular or ventricular impulses encounter diseased His-Purkinje fibers during diastolic depolarization, may contribute to post-TAVR conduction disturbances. We present an instructive case of a 71-year-old woman with severe aortic valve stenosis who developed CHB in the setting of phase 4 atrioventricular block following TAVR. Despite recovering sinus rhythm with 1:1 atrioventricular conduction within 12 hours post-procedure, she experienced recurrent ventricular standstill upon temporary pacemaker removal, ultimately requiring permanent pacemaker implantation. This case illustrates the multiple mechanisms and temporal patterns of post-TAVR conduction system disorders, the potential unreliability of early apparent conduction recovery as a predictor of durable atrioventricular conduction, and the necessity for careful and more prolonged patient monitoring before and after temporary pacemaker removal.