Left Bundle Branch Block–Induced Cardiomyopathy in a Transplanted Heart Treated With His Bundle Pacing

Abstract A 70-year-old male with prior orthotopic heart transplant developed left bundle branch block followed by new-onset left ventricular systolic dysfunction. He underwent His bundle pacing for cardiac resynchronization therapy with complete normalization of his ejection fraction. This is the first reported case of left bundle branch block–induced cardiomyopathy in a transplanted heart. (Level of Difficulty: Advanced.)