Background <p>Grafting of the left internal thoracic artery to the left anterior descending artery is the gold standard for coronary artery bypass surgery. However, the effects on cerebral hemodynamics in patients with left internal carotid artery occlusion remain unknown.</p> Case presentation <p>A 57-year-old man with complete left internal carotid artery occlusion presented with symptomatic ischemic three-vessel disease. Intraoperative echography showed increased flow in the left vertebral artery during left internal thoracic artery clamping. A composite graft was developed, using a free left internal thoracic artery and saphenous vein graft, to perform coronary artery bypass surgery. Postoperative imaging revealed no evidence of cerebral infarction.</p> Conclusions <p>Our experience suggests that a free left internal thoracic artery may be more effective than an in situ graft for patients with left internal carotid artery occlusion. Intraoperative assessment with left vertebral artery echography plays a crucial role in determining optimal bypass grafts.</p>