Double QRS Transition Due to Anodal Capture During Left Bundle Branch Area Pacing: A Case Report

Anodal capture, characterized by a different QRS morphology compared to cathodal capture, is a well-known issue in cardiac resynchronization therapy (CRT). Left bundle branch area pacing (LBBAP), a novel physiological pacing technique, is also used as a bailout strategy following failed conventional CRT implantation. In LBBAP, QRS transition, defined by a change in paced QRS morphology, serves as a key marker of successful lead placement. This case report is the first to document both high-output anodal capture and LBBAP-induced QRS transition in a single individual receiving LBBAP with an implantable cardioverter–defibrillator (ICD) as a bailout strategy for failed cardiac resynchronization therapy with defibrillator (CRT-D) implantation. Their coexistence underscores unique device optimization challenges in this emerging approach.