Persistent left-sided superior vena cava--a pacing challenge

A left sided superior vena cava (LSVC) occurs in 0.3% of the population. LSVC normally drains into the right atrium through a dilated coronary sinus. We illustrate two cases of dual chamber permanent pacemaker implantation by using (1) left subclavian vein in a 35-year-old woman with symptomatic Mobitz type II atrioventricular block; and (2) right subclavian vein in a 64-year-old man who was hospitalized with bradycardia, complete heart block, and alternating bundle branch block. After accessing the subclavian vein, the pacing leads were advanced into the LSVC, which was situated to the left of the vertebral column in the mediastinum. The leads followed the course of the LSVC medially before entering into the right atrium. Once inside the right atrium, the ventricular lead made a U-turn towards the tricuspid valve and into the right ventricle by shaping the stylet, and it was helped by right atrial contraction. An active fixation atrial lead was used in both cases to secure a satisfactory location within the right atrium. A small volume of contrast can be injected into the pacing sheath to visualize the coronary sinus opening into the right atrium, and the right ventricle. Fluoroscopy in oblique views can be helpful in guiding the atrial lead into the anteriorly positioned atrial appendage. In emergency transvenous ventricular temporary pacing where the subclavian or internal jugular vein is used, it is important to recognize the presence of a LSVC. The lead should first be directed into the right atrium and then looped back into the right ventricle. Excessive force must be avoided to prevent cardiac perforation and tamponade. If this is not successful, access through a femoral vein should be attempted.