Double superior vena cava: presentation of two cases and review of the literature.

Various anomalies in the development of the great thoracic veins of the embryo can be incidentally discovered in the normal adult. Duplication of superior vena cava (SVC) is a rare abnormality, but the most common thoracic venous congenital anomaly. We present two cases in the intensive care unit of our hospital, of asymptomatic patients who underwent an uneventful central line placement in the left subclavian vein. The track of the catheter, as shown in the X-ray, was misplaced to the left of the aorta and further investigation with computed tomography angiography confirmed a persistent left SVC. In both cases the vein drained into the coronary sinus and then to the right atrium. In the second case the echocardiography revealed a dilated coronary sinus. Double SVC can be fortuitously discovered during catheter insertion, thoracic or cardiac imaging and surgery. In most cases it drains into the right atrium, through the coronary sinus. This entity is significant to the physician because of its importance in differential diagnosis as a cause of a widened mediastinum, as well as any difficulty that can occur in the placement of a central venous catheter or a pace maker.