Rare Anomalous Left Brachiocephalic Venous Drainage Affecting Pacemaker Placement.

An 88-year-old man with severe aortic stenosis and paroxysmal atrial fibrillation presented for elective dual chamber pacemaker implantation. During the procedure, an aberrant venous system was discovered. The left brachiocephalic vein was cannulated, but attempts to advance the guidewire failed due with an accessory hemiazygos vein draining into the azygous vein. Described anomalies in upper body venous return include persistent left superior vena cava (SVC), interruption of the SVC, and anomalous course of the brachiocephalic veins. This anomaly has been described twice in the literature. Congenital anomalies of thoracic veins, although usually clinically silent, can pose challenges during vascular interventions. This case highlights the importance of recognizing these anatomic variants and the impact they can have on minimally invasive thoracic surgery such as pacemaker and central line insertion.