Abnormal origin of the left internal thoracic artery detected only by computed tomography.

The origins of the branches of the subclavian artery are known to be variable. We present the case of a 55-year-old man whose coronary artery bypass surgery necessitated the use of the internal thoracic artery as he lacked other suitable venous conduits. The left internal thoracic artery appeared to be absent on subselective subclavian angiography. Computed tomographic angiography revealed a previously undescribed anomaly: origin of the internal thoracic artery from a thyrocervical trunk arising directly from the aortic arch.