Irreversible left-ventricular lead electrical failure from conductor externalization managed with left bundle branch...

Conductor externalization is a recognized mechanism of transvenous lead failure. In left-ventricular (LV) coronary-sinus (CS) leads, irreversible electrical failure requiring extraction is uncommon. Conduction system pacing with left bundle branch area pacing (LBBAP) can provide a physiological alternative when CS re-implantation is not feasible.

A 67-year-old man with non-ischaemic cardiomyopathy and reduced LV ejection fraction (EF) secondary to infective endocarditis with severe aortic/mitral regurgitation underwent bioprosthetic aortic valve replacement with mitral repair and cardiac resynchronization therapy-defibrillator implantation in 2021 after drug-associated torsade de pointes and ventricular fibrillation arrest. He underwent transcatheter edge-to-edge mitral repair in June 2024. At routine review in October 2024, he was clinically well and asymptomatic; LV lead testing showed very high impedance (>3000 Ω), threshold 5.75 V at 1.0 ms, and intermittent loss of capture. Chest radiography showed stable lead position. At revision in March 2025, the extracted LV lead displayed conductor externalization, and CS re-implantation was precluded by a small, unwireable anterolateral branch. LBBAP was implanted with low capture threshold and stable sensing; the generator was replaced without complications. At 1-month follow-up, the LV EF was 20-25% (previously 10-15% in 2024); by August 2025 he was New York Heart Association (NYHA) class I and euvolaemic with stable weight.

This case demonstrates persistent electrical failure in LV CS lead with extraction-confirmed conductor externalization, contrasts with prior reports of electrically silent or transient disturbance, and supports LBBAP as a practical physiological option when CS re-implantation is not feasible.