左室ペースメーカーリードの導線露出による不可逆的電気的故障に対する左脚ブロック領域ペーシングによる管理：症例報告

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.