His-bundle pacing in a patient with persistent left superior vena cava.

The presence of a persistent left superior vena cava was encountered in a 53-year-old woman undergoing a dual-chamber pacemaker implant for sick sinus syndrome. Active fixation leads were used and positioned in the right atrium and right ventricle via the left superior vena cava draining into the coronary sinus. The natural course of the right ventricular lead riding up the lateral atrial wall and curving backward toward the septum as it exits from the coronary sinus os was found to facilitate the positioning of the lead tip close to the His bundle without the use of a specially designed guiding catheter.