Double QRS Transition 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 clinical case highlights the importance of recognizing both anodal capture and QRS transition in patients receiving LBBAP combined with an implantable cardioverter-defibrillator (ICD) as bailout strategy for failed cardiac resynchronization therapy with defibrillator (CRT-D) implantation, in order to optimize pacing parameters and device programming.