Cardiac resynchronization therapy through left bundle branch pacing in a patient with persistent left superior vena cava

Cardiac resynchronization therapy (CRT) is a mainstay in the treatment of heart failure with severe left ventricular dysfunction, especially in presence of left bundle branch block (LBBB). Biventricular pacing demonstrated notable results in improving prognosis and quality of life in these patients1,2, but its implantation is strictly dependent on a favorable cardiac venous anatomy to allow the delivery of a left ventricular lead into the coronary sinus (CS). Persistent left superior vena cava (LSVC) is the most common congenital thoracic venous anomaly, with prevalence from 0.2 to 3% in the general healthy population.