Coronary artery disease is an atherosclerotic disease, which often invades the carotid artery at the same time causing atheromatous plaque or even stenosis or occlusion. If there is also severe stenosis of the carotid artery, it will increase the risk of brain complications after bypass surgery, so it is necessary to deal with carotid stenosis first before considering coronary artery bypass surgery. Patients with severe carotid artery stenosis who already have dizziness, haziness and other symptoms of inadequate blood supply to the brain before surgery will further aggravate cerebral ischemia during bypass surgery (with or without extracorporeal circulation), which may prevent or delay awakening after surgery, and increase the chance of cerebral infarction (stroke) after surgery.