Conduction System Pacing-Induced Ventricular Arrhythmia: Case Report.

Left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT), combining left bundle branch area pacing (LBBAP) with a left ventricular lead, offers physiological activation and improved synchrony compared with conventional biventricular pacing. We report a 78-year-old woman with pacing-induced cardiomyopathy who underwent LOT-CRT, resulting in QRS narrowing but notable QT prolongation and T-wave inversions. On the first post-implant day, she developed ventricular fibrillation triggered by premature ventricular complexes, without reversible metabolic or ischemic cause. This case highlights the potential for early post-procedural ventricular arrhythmias in structurally compromised ventricles, underscoring the importance of vigilant monitoring and individualized risk assessment following LOT-CRT.