BACKGROUND
Cardiac resynchronization therapy can fail in the presence of anatomical variations, such as persistent left superior vena cava, which can preclude coronary sinus cannulation and left ventricular lead placement. Conduction system pacing, particularly left bundle branch area pacing, has emerged as a physiological alternative for achieving ventricular resynchronization in such anatomically challenging situations and may provide an effective solution when standard cardiac resynchronization therapy (CRT) is not feasible.
CASE REPORT
We report the case of a 78-year-old man with chronic heart failure (left ventricular ejection fraction 35%) and a history of mitral valve replacement with a bioprosthesis, tricuspid valve repair, and a bilateral Maze procedure. The patient was indicated for cardiac resynchronization therapy pacemaker (CRT-P) implantation due to sick sinus syndrome with tachy-brady arrhythmia and left bundle branch block with a QRS duration of 190 ms. Periprocedural venography revealed a persistent left superior vena cava draining into a markedly dilated coronary sinus without suitable lateral branches, preventing left ventricular lead placement. Following device implantation, the patient experienced progressive heart failure deterioration, with a decline in left ventricular ejection fraction (LVEF) to 25% and an increase in NT-proBNP to 7741 ng/L, subsequently fulfilling criteria for implantable cardioverter-defibrillator implantation. Due to unfavorable venous anatomy, conduction system pacing (CSP) was selected as an alternative strategy. A right-sided implantable cardioverter defibrillator (ICD) system with left bundle branch area pacing (LBBAP) was successfully implanted, resulting in significant QRS narrowing to 120 ms and excellent pacing parameters. At 2-month follow-up, the patient remained clinically stable (NYHA class II) with improvement in LVEF to 30-35%.
CONCLUSIONS
This case illustrates that LBBAP can provide effective ventricular activation and resynchronization when conventional CS-based CRT is not feasible due to venous anomalies. LBBAP is a safe and effective alternative in patients with PLSVC and unfavorable CS anatomy.

Keywords: Cardiac Resynchronization Therapy; Cardiology; Case Reports; Heart Failure; Persistent Left Superior Vena Cava