Coronary Artery Bypass Graft Surgery Health Article

Definition

Coronary artery bypass graft surgery is a surgical procedure in which one or more blocked coronary arteries are bypassed by a blood vessel graft to restore normal blood flow to the heart. These grafts usually come from the patient's own arteries and veins located in the leg, arm, or chest.

Purpose

Coronary artery bypass graft surgery (also called coronary artery bypass surgery [CABG] and bypass operation) is performed to restore blood flow to the heart. This relieves chest pain and ischemia, improves the patient's quality of life, and, in some cases, prolongs the patient's life. The goals of the procedure are to relieve symptoms of coronary artery disease, enable the patient to resume a normal lifestyle, and to lower the risk of a heart attack or other heart problems.

According to the American Heart Association, appropriate candidates for coronary artery bypass graft surgery include patients who:

• have blockages in at least two to three major coronary arteries, especially if the blockages are in arteries that feed the heart's left ventricle or in the left anterior descending artery
• have angina so severe that even mild exertion causes chest pain
• have poor left ventricular function
• cannot tolerate percutaneous transluminal coronary angioplasty and do not respond well to drug therapy

Demographics

Coronary artery bypass graft surgery is widely performed in the United States. It is estimated that more than 800,000 coronary artery bypass graft surgeries are performed worldwide every year. The American Heart Association reports that 519,000 coronary artery bypass graft surgeries were performed in the United States in 2000, of which 371,000 were performed on men and 148,000 on women.

Description

Coronary artery bypass graft surgery builds a detour around one or more blocked coronary arteries with a graft from a healthy vein or artery. The graft goes around the clogged artery (or arteries) to create new pathways for oxygen-rich blood to flow to the heart.

Procedure

After general anesthesia is administered, the surgeon removes the veins or prepares the arteries for grafting. If the saphenous vein is to be used for the graft, a series of incisions are made in the patient's thigh or calf. If the radial artery is to be used for the graft, incisions are made in the patient's forearm. It is important to note that the removal of veins or arteries for grafting does not deprive the area of adequate blood flow.

More commonly, a segment of the internal mammary artery is used for the graft, and the incisions are made in the chest wall. The internal mammary arteries are most commonly used because they have shown the best long-term results. Because they have their own oxygen-rich blood supply, the internal mammary arteries can usually be kept intact at their origin, then sewn to the coronary artery below the site of blockage.

The surgeon decides which grafts to use, depending on the location of the blockage, the amount of the blockage, and the size of the patient's coronary arteries.

In traditional coronary artery bypass surgery, the surgeon makes an incision down the center of the patient's chest, cuts through the breastbone, and retracts the rib cage open to expose the heart. The patient is connected to a heart-lung bypass machine, also called a cardiopulmonary bypass pump, that takes over for the heart and lungs during the surgery. During this "on-pump" procedure, the heart-lung machine removes carbon dioxide from the blood and replaces it with oxygen. A tube is inserted into the aorta to carry the oxygenated blood from the bypass machine to the aorta for circulation to the body. The heart-lung machine allows the heart's beating to be stopped, so the surgeon can operate on a still heart. Aortic clamps are used to restrict blood flow to the area of the heart where grafts will be placed so the heart is blood-free during the surgery. The clamps remain until the grafts are in place.

Some patients may be candidates for minimally invasive coronary artery bypass surgery or for off-pump bypass surgery. During minimally invasive surgery, smaller chest and graft removal incisions are used, promoting a quicker recovery and less risk of infection. Off-pump bypass surgery, also called beating heart surgery, is a surgical technique performed while the heart is still beating. The surgeon uses advanced equipment to stabilize portions of the heart and bypass the blocked artery while the rest of the heart keeps pumping and circulating blood through the body.

After the grafts are prepared, a small opening is made just below the blockage in the diseased coronary artery. Blood will be redirected through this opening once the graft is sewn in place. If a leg or arm vein is used, one end is connected to the coronary artery and the other to the aorta; if a mammary artery is used, one end is connected to the coronary artery while the other remains attached to the aorta. The procedure is repeated on as many coronary arteries as necessary. On average, three or four coronary arteries are bypassed during surgery. Blood flow is checked to assure the graft supplies adequate blood to the heart.

If the procedure was done "on-pump," electric shocks start the heart pumping again after the grafts have been completed. The heart-lung machine is turned off and the blood slowly returns to normal body temperature. After implanting pacing wires and inserting a chest tube to drain fluid, the surgeon closes the chest cavity. Sometimes a temporary pacemaker is attached to the pacing wires to regulate the heart rhythm until the patient's condition improves. After surgery, the patient is transferred to an intensive care unit for close monitoring.