This is done commonly in patients with left main coronary artery disease or three vessel disease. The internal mammary artery (located in chest) or saphenous vein (located in the leg) are used to bypass the obstruction. However, in some cases these arteries (artery used to bypass the blocked artery) may get occluded again. But the chances of reocclusion can be decreased by use of aspirin and by taking care of the risk factors. CABG is quite a safe procedure now a days with mortality rate less than one percent.