Unprecedented Complication of Left Bundle Branch Pacing

BACKGROUND: Left bundle branch pacing (LBBP) is increasingly used for physiological pacing in bradyarrhythmias and is generally safe, though rare complications may arise. CASE SUMMARY: A 72-year-old woman with sick sinus syndrome underwent LBBP with multiple challenging lead placement attempts. One attempt caused resistance during lead withdrawal. Imaging later revealed a 1.5-mm ventricular septal defect, severe mitral regurgitation from anterior mitral leaflet prolapse, and severe tricuspid regurgitation. Histopathology showed valvular tissue on the lead, suggesting chordal entrapment and septal perforation during manipulation. DISCUSSION: This case highlights a unique, previously unreported combination of ventricular septal rupture and valvular injury after LBBP. TAKE-HOME MESSAGES: Although rare, conduction system pacing can result in mechanical complications such as septal injury and mitral chordal entrapment. Monitoring of pacing parameters, including abrupt impedance changes or resistance during lead manipulation, may aid in early recognition of tissue entrapment and prevent structural damage.