<qa>  What is the large blood vessel that is attached to the heart?Patients who have coronary artery bypass graft CABG surgery must have their aorta the large blood vessel that is attached to the heart clamped with an instrument. There are two basic ways of manipulating the aorta during surgery. One way is to place a single clamp across the aorta. The other way is to place more than one clamp on the aorta in several places. Both methods are used, but it is not known if one way is better than the other. 