Coronary bypass surgery is performed on over half a million Americans each year. Bypass surgery creates a new route around the blocked vessel or vessels to maintain the proper flow of blood. The bypass may be constructed with a vein from the leg (the saphenous vein), chest (internal mammary artery, or IMA), or arm (the radial artery. One end of the vessel is grafted to the heart, while the other end is grafted to the blocked coronary artery. The entire process takes four to six hours and patients are generally kept in the intensive care unit for a few days to recover.