Your heart is located in the center of your chest. It is surrounded by your rib cage and protected by your breastbone. Your heart's job is to keep blood continually circulating throughout your body. The vessels that supply the body with oxygen-rich blood are called arteries.
The vessels that return blood to the heart are called veins. Like any other muscle in the body, the heart depends on a steady supply of oxygen rich blood. The arteries that carry this blood supply to the heart muscle are called coronary arteries.
Sometimes, these blood vessels can narrow or become blocked by deposits of fat, cholesterol and other substances collectively known as plaque. Over time, plaque deposits can narrow the vessels so much that normal blood flow is restricted. In some cases, the coronary artery becomes so narrow that the heart muscle itself is in danger.
Coronary bypass surgery attempts to correct this serious problem. In order to restore normal blood flow, the surgeon removes a portion of a blood vessel from the patient's leg or chest, most probably the left internal mammary artery and the saphenous vein.
Your doctor uses one or both of these vessels to bypass the old, diseased coronary artery and to build a new pathway for blood to reach the heart muscle. These transplanted vessels are called grafts and depending on your condition, your doctor may need to perform more than one coronary artery bypass graft.
Of course, operating on the heart is a complex and delicate process and in the case of bypass surgery, your doctor will most likely need to stop your heart before installing the graft.
During the time that your heart is not beating, a special machine, called a heart-lung machine, will take over the job of circulating and oxygenating your blood. By using this machine, your doctor is able to repair the heart without interfering with the blood flow to the rest of the body.
Following surgery, your heart will be restarted and you will be disconnected from the heart-lung machine.