Left innominate vein aneurysm finding during pacemaker lead insertion.

Thoracic vein aneurysms are very rare vascular lesions, usually detected as incidental findings. We describe the case of a patient with an advanced atrioventricular block who underwent definitive pacemaker implantation. In order to explain the difficult advancement of a pacemaker lead, vein angiography was performed during the procedure and a large innominate vein aneurysm was observed.