Unusual subclavian steal phenomenon.

A patient who had undergone myocardial revascularization with a saphenous vein graft to the left anterior descending artery and a left internal thoracic (mammary) artery graft to the 1st diagonal branch presented with an unusual form of subclavian steal syndrome. Occlusion of both the left subclavian and the left anterior descending arteries caused retrograde flow through the internal thoracic artery to the distal subclavian artery; the blood flow was supplied by the vein graft via the distal left anterior descending artery and diagonal branch.