Left superior vena cava, a remnant of embryological development

A 46-year-old Brugada syndrome patient underwent insertion of a dual-chamber implantable cardioverter- defibrillator (ICD), revealing a left-sided superior vena cava (SVC), (figure 1), running, characteristically, left from the sternum and flowing into the great cardiac vein. Following this course, the atrial lead was placed in the right atrium (RA) (figure 2, arrow, note dorsal position). The ventricular lead was inserted through the connecting anonymous vein between left and right SVC (figure 1, double arrow), into the right SVC and right ventricle (RV). The presence of a left superior vena cava results from the persistence of the embryonic left anterior cardinal vein. This anomaly is present in approximately 0.5% of the general population and in 3 to 5% of persons with other congenital heart defects, as established by autopsy.