High-density mapping-guided corrective HIS bundle pacing after failed CRT upgrade for persistent left superior vena cava.

In patients with persistent left superior vena cava (PLSVC), transvenous device implantation for cardiac resynchronization therapy (CRT) may be challenging. We present a complex case with successful, high-density electroanatomic mapping (EAM) guided corrective His bundle pacing (CHBP) following failed CRT upgrade in a patient with PLSVC, congenital heart disease, and pacing-associated heart failure. CHBP restored physiological conduction in left bundle branch block with complete conduction block leading to clinical improvement and cardiac remodeling. The presented case supports the growing evidence that EAM-guided CHBP may be considered a feasible alternative to conventional CRT when venous anatomy is not favorable for left ventricular lead implantation.