A very unusual origin of left subclavian artery.

The left internal mammary artery, a branch of the left subclavian artery, is the most commonly used arterial graft during coronary artery bypass grafting. Although extremely rare, an abnormal origin of left subclavian artery may lead to a difficult coronary angiography procedure or result in a catastrophic complication if iatrogenically occluded during a stent-graft repair of thoracic aneurysm. We present a case of an unusual anomalous origin of the left subclavian artery, which was discovered during a diagnostic coronary angiography.