Heart bypass surgery. Image 7 of 7. Surgeon using a heating device to cauterise (seal) a blood vessel. The surgeon is in the process of closing the sternum (chest bone) after coronary artery bypass graft (CABG) surgery. The wire used to stitch the sternum back together can be seen, attached to scissors. CABG is used to treat stenosis (narrowing) of coronary arteries. An artery or vein, taken from the chest or leg is grafted onto the blocked artery, restoring blood flow to the heart. Blocked arteries can cause heart pain (angina) or a myocardial infarction (heart attack), which may be fatal. For a sequence showing CABG surgery see M560/451 to M560/457.