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.
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.
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 four to six hours—sometimes longer. The average hospital stay is four to seven days. Full recovery from coronary artery bypass graft surgery takes three to four months. Within four to six weeks, people with sedentary office jobs can return to work; people with physical jobs must wait longer and sometimes change careers.
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-four percent of these procedures were performed on men and 44% on men and women under the age of 65 (1995 data). The estimated average cost of this procedure in 1995 was $44,820.
Procedure
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 is to be used, a series of incisions are made in the patient's thigh or calf. More commonly, a segment of the internal mammary artery will be used and the incisions are made in the chest wall. The surgeon then makes an 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, that 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. The procedure 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.
Success rate of coronary artery bypass graft surgery
About 90% of patients experience significant improvements after coronary artery bypass graft surgery. Patients experience full relief from chest pain and resume their normal activities in about 70% of the cases; the remaining 20% experience partial relief. In 5–10% of coronary artery bypass graft surgeries, the bypass graft stops supplying blood to the bypassed artery within one year. Younger people who are healthy except for the heart disease do well with bypass surgery. Patients who have poorer results from coronary artery bypass graft surgery include those over the age of 70, those who have poor left ventricular function, or are undergoing a repeat surgery or other procedures concurrently, and those who continue smoking, do not treat high cholesterol or other coronary risk factors, or have another debilitating disease.
Long term, symptoms recur in only about 3–4% of patients per year. Five years after 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.
Minimally invasive coronary artery bypass graft surgery
There are two new types of minimally invasive coronary artery bypass graft surgery: port-access coronary artery bypass (also called PACAB or PortCAB) and minimally 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 through small 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, a shorter recovery period, and lower costs.
Port-access coronary artery bypass enables surgeons to perform bypasses through smaller incisions. Using a video monitor to view the procedure, the surgeon passes instruments through ports in the patient's chest to perform the bypass. Mammary arteries or leg veins are used for the grafts. Minimally invasive coronary artery bypass is performed on a beating heart and is appropriate only for bypasses of one or two arteries. Small ports are made in the patient's chest, along with a small incision directly over the coronary artery to be bypassed. Generally, the surgeon uses a mammary artery for the bypass.
Early data on outcomes for port-access coronary artery bypass and minimally invasive coronary artery bypass are favorable. Mortality rates with port-access coronary artery bypass and minimally invasive coronary artery bypass are both less than 3%—about the same as in standard coronary artery bypass graft surgery. One clinical trial indicated that survival at seven years was the same in minimally invasive coronary artery bypass and standard coronary artery bypass graft surgery, but that another intervention was necessary five times more often with minimally invasive coronary artery bypass than with standard coronary artery bypass graft surgery. The American Heart Association Council on Cardio-Thoracic and Vascular Surgery feels that both procedures appear promising but that further study is needed. More data covering longer term outcomes are necessary in order to fully assess these procedures.
a healthy heart a saphenous vein graft bypassing a diseased right coronary artery (Precision Graphics)
n. A surgical procedure performed to improve blood supply to the heart by creating new routes for blood flow when one or more of the coronary arteries become obstructed. The surgery involves removing a healthy blood vessel from another part of the body, such as the leg, and grafting it onto the heart to circumvent the blocked artery.
Surgical treatment for coronary heart disease to relieve angina pectoris and prevent heart attacks. It became widely used in the 1960s. One or more blood vessels — usually an artery in the chest or a vein from the leg — are transplanted to create new paths for blood to flow from the aorta to the heart muscle, bypassing obstructed sections of the coronary arteries.
Who Performs the Procedure and Where Is It Performed?
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. The surgery is performed in a hospital.
Questions to Ask the Doctor
Why is this surgery being performed?
Am I a candidate for minimally invasive coronary artery bypass surgery?
Which technique will be used during the surgery, the "on-pump" or "off-pump" technique?
Who will be performing the surgery? How many years of experience does this surgeon have? How many other coronary artery bypass graft surgeries has this surgeon performed?
Should I take my medications the day of the surgery?
How long will I have to stay in the hospital after the surgery?
After I go home from the hospital, how long will it take me to recover from surgery?
What should I do if I experience chest discomfort or other symptoms similar to those I felt before surgery?
What types of symptoms should I report to my doctor?
How should I care for my incision?
What types of medications will I have to take after surgery?
When will I be able to resume my normal activities?
If I have had the surgery once, can I have it again to correct future blockages?
Are there any medications, foods, or activities I should avoid to prevent my symptoms from recurring?
What lifestyle changes (including diet, weight management, exercise, and activity changes) are recommended after the procedure to improve my heart health?
How often do I need to see my doctor for follow-up visits after the surgery?
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
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.
During a coronary artery bypass graft (CABG), the chest is opened to visualize the heart (A). A heart-lung machine takes over the function of the heart during the procedure. A portion of the saphenous vein of the leg is removed (B). This vessel is used to bypass a blockage of the coronary artery. It is attached from the aorta past the point of blockage (C). Another option is to bypass a blockage with the mammary artery (D). The bypass increases blood flow to the area served by the coronary artery (E). (Illustration by Argosy.)
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.
Diagnosis/Preparation
Diagnosis
The diagnosis of coronary artery disease is made after the patient's medical history is carefully reviewed, a physical exam is performed, and the patient's symptoms are evaluated. Tests used to diagnose coronary artery disease include:
blood tests to measure blood cholesterol, triglycerides, and other substances
Preparation
The individual should quit smoking or using tobacco products before the surgery. The individual needs to make the commitment to be a nonsmoker after the surgery. There are several smoking cessation programs available in the community. The individual can ask a health care provider for more information about quitting smoking.
Coronary artery bypass graft surgery should ideally be postponed for three months after a heart attack. Patients should be medically stable before the surgery, if possible.
During a preoperative appointment, usually scheduled within one to two weeks before surgery, the patient will receive information about what to expect during the surgery and the recovery period. The patient will usually meet the cardiologist, anesthesiologist, nurse clinicians, and surgeon during this appointment or just before the procedure.
If the patient develops a cold, fever, or sore throat within a few days before the surgery, he or she should notify the surgeon's office.
The evening before the surgery, the patient showers with antiseptic soap provided by the surgeon's office. After midnight, the patient should not eat or drink anything.
The patient is usually admitted to the hospital the same day the surgery is scheduled. The patient should bring a list of current medications, allergies, and appropriate medical records upon admission to the hospital.
Before the surgery, the patient is given a blood-thinning drug—usually heparin—that helps to prevent blood clots. A sedative is given the morning of surgery. The chest and the area from where the graft will be taken are shaved.
Coronary angiography will have been previously performed to show the surgeon where the arteries are blocked and where the grafts might best be positioned. Heart monitoring is initiated. The patient is given general anesthesia before the procedure.
The length of the procedure depends upon the number of arteries being bypassed, but it generally takes from three to five hours—sometimes longer.
Aftercare
Recovery in the Hospital
The patient recovers in a surgical intensive care unit for one to two days after the surgery. The patient will be connected to chest and breathing tubes, a mechanical ventilator, a heart monitor, and other monitoring equipment. A urinary catheter will be in place to drain urine. The breathing tube and ventilator are usually removed about six hours after surgery, but the other tubes usually remain in place as long as the patient is in the intensive care unit.
Drugs are prescribed to control pain and to prevent unwanted blood clotting. Daily doses of aspirin are started within six to 24 hours after the procedure.
The patient is closely monitored during the recovery period. Vital signs and other parameters such as heart sounds, oxygen, and carbon dioxide levels in arterial blood are checked frequently. The chest tube is checked to ensure that it is draining properly. The patient may be fed intravenously for the first day or two.
Chest physiotherapy is started after the ventilator and breathing tubes are removed. The therapy includes coughing, turning frequently, and taking deep breaths. Sometimes oxygen is delivered via a mask to help loosen and clear secretions from the lungs. Other exercises will be encouraged to improve the patient's circulation and prevent complications due to prolonged bed rest.
If there are no complications, the patient begins to resume a normal routine on the second day, including eating regular food, sitting up, and walking around a bit. Before being discharged from the hospital, the patient usually spends a few days under observation in a nonsurgical unit. During this time, counseling is usually provided on eating right and starting a light exercise program to keep the heart healthy.
The average hospital stay after coronary artery bypass graft surgery is five to seven days.
Recovery At Home
Incision and Skin Care
The incision should be kept clean and dry. When the skin is healed, the incision should be washed with soapy water. The scar should not be bumped, scratched, or otherwise disturbed. Ointments, lotions, and dressings should not be applied to the incision unless specific instructions have been given.
Discomfort
While the incision scar heals, which takes one to two months, it may be sore. Itching, tightness, or numbness along the incision are common. Muscle or incision discomfort may occur in the chest during activity.
Swelling or aching may occur in the legs if the saphenous vein was used for the graft. Special support stockings may be needed to decrease leg swelling after surgery. While sitting, the patient should not cross the legs and the feet should be elevated. Walking daily, even if the legs are swollen, will help improve circulation and reduce swelling.
Lifestyle Changes
The patient needs to make several lifestyle changes after surgery, including:
Quitting smoking. Smoking causes damage to the bypass grafts and other blood vessels, increases the patient's blood pressure and heart rate, and decreases the amount of oxygen available in the blood.
Managing weight. Maintaining a healthy weight, by watching portion sizes and exercising, is important. Being overweight increases the work of the heart.
Participating in an exercise program. The exercise program is usually tailored for the patient, who will be encouraged to participate in a cardiac rehabilitation program supervised by exercise professionals.
Making dietary changes. Patients should eat a lot of fruits, vegetables, grains, and non-fat or low-fat dairy products, and reduce fats to less than 30% of all calories.
Taking medications as prescribed. Aspirin and other heart medications may be prescribed, and the patient may need to take these medications for life.
Following up with health care providers. The patient must schedule follow-up visits to determine how effective the surgery was, to confirm that progressive exercise is safe, and to monitor his or her recovery and control risk factors.
Risks
Coronary artery bypass graft surgery is major surgery and patients may experience any of the normal complications associated with major surgery and anesthesia, such as the risk of bleeding, pneumonia, or infection. Possible complications include:
blood clots that can lead to a stroke or heart attack
kidney failure
depression or severe mood swings
possible short-term memory loss, difficulty thinking clearly, and problems concentrating for long periods (These effects generally subside within six months after surgery.)
There is a higher risk for complications in patients who:
are heavy smokers
have a history of lung, kidney, or metabolic diseases
Full recovery from coronary artery bypass graft surgery takes two to three months and is a gradual process. Upon release from the hospital, the patient will feel weak because of the extended bed rest in the hospital. Within a few weeks, the patient should begin to feel stronger.
Most patients are able to drive in about three to eight weeks, after receiving approval from their physician. Sexual activity can generally be resumed in three to four weeks, depending on the patient's rate of recovery.
It takes about six to eight weeks for the sternum to heal. During this time, the patient should not perform activities that cause pressure or weight on the breastbone or tension on the arms and chest. Pushing and pulling heavy objects (as in mowing the lawn) should be avoided and lifting objects more than 20 lbs (9 kg) is not permitted. The patient should not hold his or her arms above shoulder level for a long period of time, such as when doing household chores. The patient should try not to stand in one place for longer than 15 minutes. Stair climbing is permitted unless other instructions have been given.
Within four to six weeks, people with sedentary office jobs can return to work; people with physical jobs such as construction work or jobs requiring heavy lifting must wait longer (up to 12 weeks) or may have to change careers.
About 90% of patients experience significant improvements after coronary artery bypass graft surgery. Patients experience full relief from chest pain and resume their normal activities in about 70% of the cases; the remaining 20% experience partial relief.
For most people, the graft remains open for about 10–15 years.
Coronary artery bypass surgery does not prevent coronary artery disease from recurring. Therefore, lifestyle changes are strongly recommended and medications are prescribed to reduce this risk. About 40% of patients have a new blockage within 10 years after surgery and require a second bypass, change in medication, or an interventional procedure.
Morbidity and Mortality Rates
The risk of death during coronary artery bypass graft surgery is 2–3%.
In 5–10% of coronary artery bypass graft surgeries, the bypass graft stops supplying blood to the bypassed artery within one year. Younger people who are healthy except for the heart disease achieve good results with bypass surgery. Patients who have poorer results from coronary artery bypass graft surgery include those over the age of 70, those who have poor left ventricular function, are undergoing a repeat surgery or other procedures concurrently, and those who continue smoking, do not treat high cholesterol or other coronary risk factors, or have another debilitating disease.
Over the long term, symptoms recur in only about 3–4% of patients per year. Five years after coronary artery bypass graft surgery, survival expectancy is 90%, at 10 years it is about 85%, at 15 years it is about 55%, and at 20 years it is about 40%.
Angina recurs in about 40% of patients after 10 years. In most cases, it is less severe than before the surgery and can be controlled with 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.
Alternatives
All patients with coronary artery disease can help improve their condition by making lifestyle changes such as quitting smoking, losing weight if they are overweight, eating healthy foods, reducing blood cholesterol, exercising regularly, and controlling diabetes and high blood pressure.
All patients with coronary artery disease should be prescribed medications to treat their condition. Antiplatelet medications such as aspirin or clopidogrel (Plavix) are usually recommended. Other medications used to treat angina may include beta blockers, nitrates, and angiotensin-converting enzyme (ACE) inhibitors. Medications may also be prescribed to lower lipoprotein levels, since elevated lipoprotein levels have been associated with an increased risk of cardiovascular problems.
Treatment with vitamin E is not recommended because it does not lower the rate of cardiovascular events in people with coronary artery disease. Although antioxidants such as vitamin C, beta-carotene, and probucol show promising results, they are not recommended for routine use. Treatment with folic acid and vitamins B6 and B12 lowers homocysteine levels (reducing the risk for cardiovascular problems), but more studies are needed to determine if lowered homocysteine levels correlate with a reduced rate of cardiovascular problems in treated patients.
Less invasive, nonsurgical interventional procedures—such as balloon angioplasty, stent placement, rotoblation, atherectomy, or brachytherapy—can be performed to open a blocked artery. These procedures may be the appropriate treatment for some patients before coronary artery bypass graft surgery is considered.
Enhanced external counterpulsation (EECP) may be a treatment option for patients who are not candidates for interventional procedures or coronary artery bypass graft surgery. During EECP, a set of cuffs is wrapped around the patient's calves, thighs, and buttocks. These cuffs gently but firmly compress the blood vessels in the lower limbs to increase blood flow to the heart. The inflation and deflation of the cuffs are electronically synchronized with the heartbeat and blood pressure using electrocardiography and blood pressure monitors. EECP may encourage blood vessels to open small channels to eventually bypass blocked vessels and improve blood flow to the heart. Not all patients are candidates for this procedure, and treatments, lasting one to two hours, must be repeated about five times a week for up to seven weeks.
Resources
Books
American Heart Association. "Considering Surgery or Other Interventions." In Guide to Heart Attack Treatment, Recovery, Prevention. New York: Time Books, 1996.
Barry, Frank. The Healthy Heart Formula: The Powerful, New,Commonsense Approach to Preventing and Reversing Heart Disease. New York: John Wiley & Sons, 1998.
DeBakey, Michael E., and Antonio M. Gotto Jr. "Surgical Treatment of Coronary Artery Disease." In The New Living Heart. Holbrook, MA: Adams Media Corporation, 1997.
McGoon, Michael D., and Bernard J. Gersh. Mayo ClinicHeart Book: The Ultimate Guide to Heart Health, Second Edition. New York: William Morrow and Co., Inc., 2000.
Texas Heart Institute. "Heart Surgery." In Texas Heart InstituteHeart Owner's Handbook. New York: John Wiley & Sons, 1995.
Topol, Eric J. Cleveland Clinic Heart Book: The DefinitiveGuide for the Entire Family from the Nation's Leading Heart Center. New York: Hyperion, 2000.
Trout, Darrell, and Ellen Welch. Surviving with Heart: TakingCharge of Your Heart Care. Golden, CO: Fulcrum Publishing, 2002.
Periodicals
Eagle, K. A., et al. "ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery: Executive Summary and Recommendations: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1991 Guidelines for Coronary Artery Bypass Graft Surgery)." Circulation 100 (1999): 1464–1480.
Mullany, Charles J. "Coronary Artery Bypass Surgery." Circulation 107 (2003): e21–e22.
Sabik, Joseph. Off-Pump Bypass Surgery: Improving Outcomes for Coronary Artery Bypass Surgery. Cleveland Clinic Heart Center, The Cleveland Clinic Foundation. November 2001.
Organizations
American College of Cardiology. Heart House. 9111 Old Georgetown Rd., Bethesda, MD 20814-1699. (800) 253-4636, ext. 694, or (301) 897-5400. http://www.acc.org.
American Heart Association. 7272 Greenville Ave., Dallas, TX 75231. (800) 242-8721 or (214) 373-6300. http://www.americanheart.org.
The Cleveland Clinic Heart Center, The Cleveland Clinic Foundation. 9500 Euclid Avenue, F25, Cleveland, Ohio, 44195. (800) 223-2273, ext. 46697, or (216) 444-6697. http://www.clevelandclinic.org/heartcenter.
National Heart, Lung, and Blood Institute. National Institutes of Health. Building 1. 1 Center Dr., Bethesda, MD 20892. E-mail: NHLBIinfo@rover.nhlbi. http://www.nhlbi.nih.gov.
Texas Heart Institute. Heart Information Service. P.O. Box 20345, Houston, TX 77225-0345. http://www.tmc.edu/thi.
Other
The Heart: An Online Exploration. The Franklin Institute Science Museum. 222 North 20th Street, Philadelphia, PA, 19103. (215) 448-1200. http://sln2.fi.edu/biosci/heart.html.
A surgical procedure to restore normal blood supply to the heart by creating new routes for the blood to travel into the heart when one or both of the coronary arteries have become clogged or obstructed (possibly due to atherosclerosis). These new routes are created by removing blood vessels from another part of the body (most often the veins of the leg) and grafting them onto the heart to bypass the clogged arteries.
Often, people will call this kind of surgery a double, triple, or quadruple bypass, referring to the number of diseased coronary arteries that had to be bypassed during the operation.
Early in a coronary artery bypass surgery during vein harvesting from the legs (left of image) and the establishment of bypass (placement of the aorticcannula) (bottom of image). The perfusionist and heart-lung machine (HLM) are on the upper right. The patient's head (not seen) is at the bottom.
Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.
Heart saphenous coronary grafts
Coronary artery bypass surgery, also coronary artery bypass graft (CABG) surgery, and colloquially heart bypass or bypass surgery is a surgical procedure performed to relieve angina and reduce the risk of death from coronary artery disease. Arteries or veins from elsewhere in the patient's body are grafted to the coronary arteries to bypass atheroscleroticnarrowings and improve the blood supply to the coronary circulation supplying the myocardium (heart muscle). This surgery is usually performed with the heart stopped, necessitating the usage of cardiopulmonary bypass; techniques are available to perform CABG on a beating heart, so-called "off-pump" surgery.
The first coronary artery bypass surgery was performed in the United States on May 2, 1960 at the Albert Einstein College of Medicine-Bronx Municipal Hospital Center by a team led by Dr. Robert Goetz and the thoracic surgeon, Dr. Michael Rohman with the assistance of Dr. Jordan Haller and Dr. Ronald Dee.[1][2] But in this technique the vessels are held together with circumferential ligatures over an inserted metal ring. The internal mammary artery was used as the donor vessel and was anastomosed to the right coronary artery. The actual anastomosis with the Rosenbach ring took fifteen seconds and did not require Cardio-Pulmonary bypass. The disadvantage of using the internal mammary artery was that, at autopsy nine months later, the anastomosis was open, but an atheromatous plaque had occluded the origin of the internal mammary that was used for the bypass.
This technique was quickly superseded by Dr. René Favaloro who pioneered the bypass grafting procedure in 1967 [4] His new technique used a saphenous veinautograft to replace a stenotic segment of the right coronary artery. He later began to use the saphenous vein as a bypassing channel and become instantly successful. This is the typical bypass graft technique we know today. Soon Dr Dudley Johnson extended the bypass to include left coronary arterial systems. [3] In 1968, Doctors Charles Bailey, Teruo Hirose and George Green used the internal mammary artery instead of the saphenous vein for the grafting. [3]
Terminology
There are many variations on terminology, in which one or more of 'artery', 'bypass' or 'graft' is left out. The most frequently used acronym for this type of surgery is CABG (pronounced 'cabbage'),[5] pluralized as CABGs (pronounced 'cabbages'). More recently the term aortocoronary bypass (ACB) has come into popular use. CAGS (Coronary Artery Graft Surgery, pronounced phonetically) should not be confused with Coronary Angiography (CAG).
Arteriosclerosis is a common arterial disorder characterized by thickening, loss of elasticity, and calcification of arterial walls, resulting in a decreased blood supply.
Atherosclerosis is a common arterial disorder characterized by yellowish plaques of cholesterol, lipids, and cellular debris in the inner layer of the walls of large and medium-sized arteries.
Number of bypasses
The terms single bypass, double bypass, triple bypass, quadruple bypass and quintuple bypass refer to the number of coronary arteries bypassed in the procedure. In other words, a double bypass means two coronary arteries are bypassed (e.g. the left anterior descending (LAD) coronary artery and right coronary artery (RCA)); a triple bypass means three vessels are bypassed (e.g. LAD, RCA, left circumflex artery (LCX)); a quadruple bypass means four vessels are bypassed (e.g. LAD, RCA, LCX, first diagonal artery of the LAD) while quintuple means five. Bypass of more than four coronary arteries is uncommon.
A greater number of bypasses does not imply a person is "sicker," nor does a lesser number imply a person is "healthier."[6] A person with a large amount of coronary artery disease (CAD) may receive fewer bypass grafts owing to the lack of suitable "target" vessels. A coronary artery may be unsuitable for bypass grafting if it is small (< 1 mm or < 1.5 mm depending on surgeon preference), heavily calcified (meaning the artery does not have a section free of CAD) or intramyocardial (the coronary artery is located within the heart muscle rather than on the surface of the heart). Similarly, a person with a single stenosis ("narrowing") of the left main coronary artery requires only two bypasses (to the LAD and the LCX). However, a left main lesion places a person at the highest risk for death from a cardiac cause.[citation needed]
The surgeon reviews the coronary angiogram prior to surgery and identifies the lesions (or "blockages") in the coronary arteries. The surgeon will estimate the number of bypass grafts prior to surgery, but the final decision is made in the operating room upon examination of the heart.
Indications for CABG
Several alternative treatments for coronary artery disease exist. They include:
Both PCI and CABG are more effective than medical management at relieving symptoms,[7] (e.g. angina, dyspnea, fatigue). CABG is superior to PCI for some patients with multivessel CAD[8][9]
The Surgery or Stent (SoS) trial was a randomized controlled trial that compared CABG to PCI with bare-metal stents. The SoS trial demonstrated CABG is superior to PCI in multivessel coronary disease.[8]
The SYNTAX trial was a randomized controlled trial of 1800 patients with multivessel coronary disease, comparing CABG versus PCI using drug-eluting stents (DES). The study found that rates of major adverse cardiac or cerebrovascular events at 12 months were significantly higher in the DES group (17.8% versus 12.4% for CABG; P=0.002). [9] This was primarily driven by higher need for repeat revascularization procedures in the PCI group with no difference in repeat infarctions or survival. Higher rates of strokes were seen in the CABG group.
The FREEDOM (Future Revascularization Evaluation in Patients With Diabetes Mellitus—Optimal Management of Multivessel Disease) trial will compare CABG and DES in patients with diabetes. The registries of the nonrandomized patients screened for these trials may provide as much robust data regarding revascularization outcomes as the randomized analysis.[10]
A study comparing the outcomes of all patients in New York state treated with CABG or percutaneous coronary intervention (PCI) demonstrated CABG was superior to PCI with DES in multivessel (more than one diseased artery) coronary artery disease (CAD). Patients treated with CABG had lower rates of death and of death or myocardial infarction than treatment with a coronary stent. Patients undergoing CABG also had lower rates of repeat revascularization.[11] The New York State registry included all patients undergoing revascularization for coronary artery disease, but was not a randomized trial, and so may have reflected other factors besides the method of coronary revascularization.
The 2004 ACC/AHA CABG guidelines state CABG is the preferred treatment for:[12]
Disease of all three coronary vessels (LAD, LCX and RCA).
Diffuse disease not amenable to treatment with a PCI.
The 2005 ACC/AHA guidelines further state: CABG is the likely the preferred treatment with other high-risk patients such as those with severe ventricular dysfunction (i.e. low ejection fraction), or diabetes mellitus.[12]
Prognosis
Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10–15 years. In general, CABG improves the chances of survival of patients who are at high risk (meaning those presenting with angina pain shown to be due to ischemic heart disease), but statistically after about 5 years the difference in survival rate between those who have had surgery and those treated by drug therapy diminishes. Age at the time of CABG is critical to the prognosis, younger patients with no complicating diseases have a high probability of greater longevity. The older patient can usually be expected to suffer further blockage of the coronary arteries.[citation needed]
Procedure (Simplified)
The patient is brought to the operating room and moved on to the operating table.
An anaesthetist places a variety of intravenous lines and injects an induction agent (usually propofol) to render the patient unconscious.
In the case of "off-pump" surgery, the surgeon places devices to stabilize the heart.
If the case is "on-pump", the surgeon sutures cannulae into the heart and instructs the perfusionist to start cardiopulmonary bypass (CPB). Once CPB is established, the surgeon places the aortic cross-clamp across the aorta and instructs the perfusionist to deliver cardioplegia to stop the heart.
The heart is restarted; or in "off-pump" surgery, the stabilizing devices are removed. In some cases, the Aorta is partially occluded by a C-shaped clamp, the heart is restarted and suturing of the grafts to the aorta is done in this partially occluded section of the aorta while the heart is beating.
The sternum is wired together and the incisions are sutured closed.
The patient is moved to the intensive care unit (ICU) to recover. After awakening and stabilizing in the ICU (approximately 1 day), the person is transferred to the cardiac surgery ward until ready to go home (approximately 4 days).
The choice of conduits is highly dependent upon the particular surgeon and institution. Typically, the left internal thoracic artery (LITA) (previously referred to as left internal mammary artery or LIMA) is grafted to the left anterior descending artery and a combination of other arteries and veins is used for other coronary arteries. The right internal thoracic artery (RITA), the great saphenous vein from the leg and the radial artery from the forearm are frequently used. The right gastroepiploic artery from the stomach is infrequently used given the difficult mobilization from the abdomen.
Graft patency
Grafts can become diseased and may occlude in the months to years after bypass surgery is performed. Patency is a term used to describe the chance that a graft remain open. A graft is considered patent if there is flow through the graft without any significant (>70% diameter) stenosis in the graft.
Graft patency is dependent on a number of factors, including the type of graft used (internal thoracic artery, radial artery, or great saphenous vein), the size or the coronary artery that the graft is anastomosed with, and, of course, the skill of the surgeon(s) performing the procedure. Arterial grafts (e.g. LITA, radial) are far more sensitive to rough handling than the saphenous veins and may go into spasm if handled improperly.
Generally the best patency rates are achieved with the in-situ (the proximal end is left connected to the subclavian artery) left internal thoracic artery with the distal end being anastomosed with the coronary artery (typically the left anterior descending artery or a diagonal branch artery). Lesser patency rates can be expected with radial artery grafts and "free" internal thoracic artery grafts (where the proximal end of the thoracic artery is excised from its origin from the subclavian artery and re-anastomosed with the ascending aorta). Saphenous vein grafts have worse patency rates, but are more available, as the patients can have multiple segments of the saphenous vein used to bypass different arteries.
Veins that are used either have their valves removed or are turned around so that the valves in them do not occlude blood flow in the graft. LITA grafts are longer-lasting than vein grafts, both because the artery is more robust than a vein and because, being already connected to the arterial tree, the LITA need only be grafted at one end. The LITA is usually grafted to the left anterior descending coronary artery (LAD) because of its superior long-term patency when compared to saphenous vein grafts.[13][14]
Sternal Precautions
Patients undergoing coronary artery bypass surgery will have to avoid certain things for eight to 12 weeks to reduce the risk of opening the incision. These are called sternal precautions. First, patients need to avoid using their arms excessively, such as pushing themselves out of a chair or reaching back before sitting down. To avoid this, patients are encouraged to build up momentum by rocking several times in their chair before standing up. Second, patients should avoid lifting anything in excess of 5-10 pounds. A gallon (U.S.) of milk weighs approximately 8.5 pounds, and is a good reference point for weight limitations. Finally, patients should avoid overhead activities with their hands, such as reaching for sweaters from the top shelf of a closet or reaching for plates or cups from the cupboard.
Complications
People undergoing coronary artery bypass are at risk for the same complications as any surgery, plus some risks more common with or unique to CABG.
CABG associated
Postperfusion syndrome (pumphead), a transient neurocognitive impairment associated with cardiopulmonary bypass. Some research shows the incidence is initially decreased by off-pump coronary artery bypass, but with no difference beyond three months after surgery. A neurocognitive decline over time has been demonstrated in people with coronary artery disease regardless of treatment (OPCAB, conventional CABG or medical management). However, recent research suggests that the cognitive decline is not caused by CABG but is rather a consequence of vascular disease.[15]
Randomized Controlled Trial (RCT) including Placebo
While there have been a handful of RCTs[8][9] comparing CABG with other surgical procedures, an exhaustive review of the medical literature reported in 2002 found no RCT had ever been conducted to demonstrate the efficacy of CABG to that of placebo.[16] In fact, as Daniel Moerman has pointed out the combined results of two RCTs comparing an earlier surgical procedure for angina - bilateral internal mammary artery ligation (BIMAL) - to a sham surgery clearly show that patients "experienced significant subjective improvement," with both BIMAL (67% substantial improvement) and the sham procedure (82% substantial improvement).[17] Surgery as a meaningful experience (placebo effect) was most likely the cause of improvement for patients in both of these studies with the sham surgical procedure actually proving slightly more effective.
^ abc Nirav J. Mehta, MD and Ijaz A. Khan, MD Houston Division of Cardiology, Creighton University School of Medicine, Omaha, Nebraska 68131,"Cardiology's 10 Greatest Discoveries of the 20th Century", FACC, 2002, Texas Heart Institute Journal, 29(3):164-171, accessed online on 2 Jan 2009 at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=124754
^ Nirav J. Mehta, MD and Ijaz A. Khan, MD Houston Division of Cardiology, Creighton University School of Medicine, Omaha, Nebraska 68131,"Cardiology's 10 Greatest Discoveries of the 20th Century", FACC, 2002, Texas Heart Institute Journal, 29(3):164-171, accessed online on 2 Jan 2009 at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=124754
^Ohki S, Kaneko T, Satoh Y, et al. (2002). "[Coronary artery bypass grafting in octogenarian]" (in Japanese). Kyobu geka. The Japanese journal of thoracic surgery55 (10): 829–33; discussion 833–6. PMID12233100.
^Rihal C, Raco D, Gersh B, Yusuf S (2003). "Indications for coronary artery bypass surgery and percutaneous coronary intervention in chronic stable angina: review of the evidence and methodological considerations". Circulation108 (20): 2439–45. doi:10.1161/01.CIR.0000094405.21583.7C. PMID14623791.Full Free Text.
^ abcSoS Investigators (2002). "Coronary artery bypass surgery versus percutaneous coronary intervention with stent implantation in patients with multivessel coronary artery disease (the Stent or Surgery trial): a randomised controlled trial". Lancet360 (9338): 965–70. doi:10.1016/S0140-6736(02)11078-6. PMID12383664.
^ abcSerruys PW, Morice M-C, Kappetein AP, et al. (2009). "Percutaneous coronary intervention versus coronary-artery bypass grafting for severe coronary artery disease". N Engl J Med. doi:10.1056/NEJMoa0804626.
^Hannan EL, Wu C, Walford G, et al. (2008). "Drug-eluting stents vs. coronary-artery bypass grafting in multivessel coronary disease". N. Engl. J. Med.358 (4): 331–41. doi:10.1056/NEJMoa071804. PMID18216353.
^ abEagle KA, Guyton RA, Davidoff R, et al. (2004). "ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery)". Circulation110 (14): e340–437. PMID15466654.
^ Kitamura S, Kawachi K, Kawata T, Kobayashi S, Mizuguchi K, Kameda Y, Nishioka H, Hamada Y, Yoshida Y. [Ten-year survival and cardiac event-free rates in Japanese patients with the left anterior descending artery revascularized with internal thoracic artery or saphenous vein graft: a comparative study] Nippon Geka Gakkai Zasshi. 1996 Mar;97(3):202-9. PMID 8649330.
^ Arima M, Kanoh T, Suzuki T, Kuremoto K, Tanimoto K, Oigawa T, Matsuda S. Serial Angiographic Follow-up Beyond 10 Years After Coronary Artery Bypass Grafting. Circ J. 2005 Aug;69(8):896-902. PMID 16041156. Free Full Text.
