Septal Branch Occlusion Leading to Complete Heart Block Post-Percutaneous Intervention: A Cautionary Tale in Left Bundle Branch Block Patients.

A 66-year-old man with a baseline electrocardiogram (ECG) showing left bundle branch block developed persistent complete atrioventricular block following stent placement in the proximal left anterior descending artery (LAD), necessitating permanent pacemaker implantation. The complication is believed to have resulted from occlusion of the second septal branch, which likely supplied the right bundle of the His system. During elective interventions targeting the LAD in patients with pre-existing conduction abnormalities, it is crucial to maintain adequate blood flow to the septal perforators.