JACC Case Rep. 2026 Sep 19:110343. doi: 10.1016/j.jaccas.2026.110343. Online ahead of print.
ABSTRACT
CASE BACKGROUND: A 61-year-old man with a mechanical aortic valve developed Staphylococcus aureus bacteremia. His electrocardiogram showed sinus rhythm with atrioventricular Wenckebach and phase 4 left bundle branch block. He was subsequently found to have a peri-aortic root abscess that was likely eroding not only into the atrioventricular node, but into the left bundle fibers as well.
TAKE-HOME MESSAGES: Phase 4 block is a pause-dependent conduction block that reflects underlying His-Purkinje system disease. During a critical pause, spontaneous phase 4 depolarization in a diseased His-Purkinje system allows more sodium channels to become inactivated, reducing excitability and resulting in transient conduction block.
PMID:42763808 | DOI:10.1016/j.jaccas.2026.110343