Coronary artery bypass graft surgery
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 (the inability of tissue to function due to insufficient blood supply), improves the patient's quality of life,and in some cases, prolongs the patient's life. The goals of the procedure are to enable the patient to resume a normal lifestyle and to lower the risk of a heart attack.
The decision to perform coronary artery bypass graft surgery is a complex one, and there is some disagreement among experts as to when it is indicated. Many experts feel that it has been performed too frequently in the United States. According to the American Heart Association, appropriate candidates or coronary artery bypass graft surgery include patients with blockages in at leastthree major coronary arteries, especially if the blockages are in arteries that feed the heart's left ventricle; patients with angina so severe that evenmild exertion causes chest pain; and patients who cannot tolerate other procedures and do not respond well to drug therapy. It is well accepted that coronary artery bypass graft surgery is the treatment of choice for patients withsevere coronary artery disease (three or more diseased arteries with impaired function in the left ventricle).
Coronary artery bypass graft surgery is major surgery performed in a hospital. The length of the procedure depends upon the number of arteries being bypassed, but it generally takes from 4 to 6 hours--sometimes longer. The averagehospital stay is 4 to 7 days. Full recovery from coronary artery bypass graftsurgery takes 3 to 4 months.
Coronary artery bypass graft surgery is widely performed in the United States. The American Heart Association estimates that 573,000 coronary artery bypass graft surgeries were performed on 363,000 patients in 1995. Seventy 4% of these procedures were performed on men and 44% on men and women under the ageof 65 (1995 data).
The surgery team for coronary artery bypass graft surgery includes the cardiovascular surgeon, assisting surgeons, a cardiovascular anesthesiologist, a perfusion technologist (who operates the heart-lung machine), and specially trained nurses. After general anesthesia is administered, the surgeon removes the veins or prepares the arteries for grafting. If the saphenous vein (long vein in the leg) is to be used, a series of incisions are made in the patient'sthigh or calf. More commonly, a segment of the internal mammary artery willbe used, and the incisions are made in the chest wall. The surgeon then makesan incision from the patient's neck to navel, saws through the breastbone, and retracts the rib cage open to expose the heart. The patient is connected to a heart-lung machine, also called a cardiopulmonary bypass pump, which cools the body to reduce the need for oxygen and takes over for the heart and lungs during the procedure. The heart is then stopped and a cold solution of potassium-enriched normal saline is injected into the aortic root and the coronary arteries to lower the temperature of the heart, which prevents damage to the tissue.
Next, 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 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. Theprocedure is repeated on as many coronary arteries as necessary. Most patients who have coronary artery bypass graft surgery have at least three grafts done during the procedure.
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 electrodes (if needed) and inserting a chest tube, the surgeon closes the chest cavity.
Long term, symptoms recur in only about 3-4% of patients per year. Five yearsafter coronary artery bypass graft surgery, survival expectancy is 90%, at 10 years it is about 80%, at 15 years it is about 55%, and at 20 years it is about 40%.
Angina recurs in about 40% of patients after about 10 years. In most cases, it is less severe than before the surgery and can be controlled by drug therapy. In patients who have had vein grafts, 40% of the grafts are severely obstructed 10 years after the procedure. Repeat coronary artery bypass graft surgery may be necessary, and is usually less successful than the first surgery.
There are two new types of minimally invasive coronary artery bypass graft surgery: port-access coronary artery bypass (also called PACAB or PortCAB) andminimally invasive coronary artery bypass (also called MIDCAB). These procedures are minimally invasive because they do not require the neck-to-navel incision, sawing through the breastbone, or opening the rib cage to expose the heart. Both procedures enable surgeons to work on the coronary arteries throughsmall chest holes called ports and other small incisions. Port-access coronary artery bypass requires the use of a heart-lung machine but minimally invasive coronary artery bypass does not. Advantages of these procedures over standard coronary artery bypass graft surgery include a shorter hospital stay, ashorter recovery period, and lower costs. Still, the American Heart Association Council on Cardio-Thoracic and Vascular Surgery feels that both proceduresappear promising but that further study is needed.
Coronary artery bypass graft surgery is major surgery and patients may experience any of the complications associated with major surgery. The risk of death during coronary artery bypass graft surgery is 2-3%. Possible complicationsinclude graft closure and development of blockages in other arteries, long-term development of atherosclerotic disease of saphenous vein grafts, abnormalheart rhythms, high or low blood pressure, blood clots that can lead to a stroke or heart attack, infections, and depression. There is a higher risk forcomplications in patients who are heavy smokers, patients who have serious lung, kidney, or metabolic problems, or patients who have a reduced supply of blood to the brain.