Left Bundle Branch-Optimized Cardiac Resynchronization Therapy in a Patient with a Carillon Annuloplasty Device: Challenges and Solutions.

Cardiac resynchronization therapy (CRT) improves outcomes in heart failure, but prior interventions like percutaneous mitral annuloplasty may hinder lead placement. We present a 70-year-old male with ischemic cardiomyopathy and severe functional mitral regurgitation who previously received a Carillon device. Due to coronary sinus inaccessibility, left bundle branch area pacing optimized cardiac resynchronization therapy (LOT-CRT) was performed. The procedure was successful, with improved QRS duration, echocardiographic findings, and clinical status. This case highlights LOT-CRT as a viable alternative in patients with challenging anatomy, offering physiological pacing when conventional CRT is not feasible.