Coronary Artery Bypass Surgery - Heart Surgery: Heart Disease

Content provided by the Faculty of the Harvard Medical School

Coronary artery bypass surgery

Since the 1970s, coronary artery bypass surgery has become one of the most common treatments for heart disease. The principle behind coronary artery bypass surgery is to construct a new channel so blood can get around blockages in the coronary arteries. The cardiac surgeon takes a length of blood vessel from elsewhere in the body and places it so that it can shunt blood around the narrowed or blocked coronary artery. The grafted vessel thus permits blood to bypass the blockage, so the heart muscle ordinarily supplied by that coronary artery can once more receive nourishment.

Coronary artery bypass surgery may be a better choice for patients with severe multivessel disease; clinical trials have shown that it also relieves the pain of angina more effectively on a long-term basis than angioplasty alone or angioplasty with stent insertion. One thing to keep in mind, however, is that coronary artery bypass surgery does not cure the underlying disease — atherosclerosis — and so angina may return 5 to 10 years after the operation, as arteries again become clogged with plaque. (This is why it's so important to adhere to a diet, exercise, and medication strategy to reduce the risk of this happening. See "Recognizing and reducing risk factors.")

Several options in coronary artery bypass surgery now exist. The old standby is conventional open heart surgery, known medically as coronary artery bypass grafting. In addition, two so-called minimally invasive procedures have gained greater acceptance and are being used more often: beating-heart surgery and minimally invasive bypass surgery. The procedure you undergo will depend largely on the nature and extent of your heart disease, your overall health, and your surgeon's expertise.

What happens during coronary artery bypass surgery

In most forms of coronary artery bypass surgery, you receive general anesthesia. The surgeon makes a large incision and cuts through the breastbone to gain access to the heart. The beating of the heart is usually stopped so that the surgeon doesn't have to perform surgery on a heart that's constantly moving. A heart-lung machine pumps oxygen-rich blood through the body, temporarily substituting for the heart.

The surgeon takes a vein or an artery from another part of your body and sutures that vessel into place to reroute blood around the blocked artery. The replacement vessel might be an internal mammary artery taken from your chest, a saphenous vein taken from your leg, or even a radial artery from your arm. Whatever artery or vein is used is a "spare" vessel. You will suffer no ill effects because that piece of artery or vein has been removed.

If the grafted vessel is a vein from a leg or arm, one end is attached to the aorta and the other is sewn onto the diseased coronary artery, beyond the blockage. When a mammary artery is used, the upper end is usually left in place at the aorta and the lower open end is attached to the diseased coronary artery, below the blockage.

After the surgery is completed, your heart is started again, and you are taken off the heart-lung machine. Some people stay in the hospital for just 4–5 days, but many stay 6–10 days or, if they have complications, even longer. Within a day or two of surgery, the doctor will probably ask you to get up and walk. You might also be scheduled for a cardiac rehabilitation program, which you will attend after leaving the hospital. Cardiac rehabilitation helps you and your heart gain strength. It also teaches you heart-healthy practices that will help protect you from future heart disease, such as observing a low-fat diet and exercising regularly.

If your job doesn't require much exertion, you can probably return to work in about two months. However, people who do heavy labor must wait longer or, in some cases, must find jobs that aren't as physically demanding.

Keeping vessels clear after surgery

Coronary artery bypass surgery is very effective in controlling the symptoms of coronary artery disease. After surgery, people often feel as if they've been given a new lease on life. But coronary artery bypass surgery doesn't cure coronary artery disease. Angina can recur, either from the buildup of plaque in arteries that weren't bypassed or because blockages form in the grafts. Combating such problems requires dietary and lifestyle changes, such as exercising regularly and not smoking, as well as aggressive efforts to control cholesterol through medication. To maximize your chances of recovery, the experts recommend these steps:

A daily aspirin. You should begin taking a daily aspirin within 48 hours of your bypass operation in order to reduce the risk of your grafted vein closing, as well as to lower your chance of heart attack, stroke, kidney failure, or death. Dosage varies from 100 mg to 325 mg per day. If you are unable to tolerate or respond to aspirin, your doctor will recommend an alternative antiplatelet therapy, but aspirin is the treatment of choice.

Statin therapy. Almost everyone undergoing a bypass operation should take a statin to lower LDL cholesterol. (The only exceptions are people who cannot take statins for some other reason; in that case, work with your doctor to find another way to lower LDL.) The NCEP recommends that people undergoing a bypass operation (and all others at high risk for heart attacks) should aim for LDL levels under 100 mg/dL.

This recommendation is supported by the Post-Coronary Artery Bypass Graft Trial, a large clinical study which found that people who kept their LDL under 100 mg/dL developed atherosclerosis in an average of 29% of their grafts, compared with 39% of grafts in people who achieved LDL levels under 140 mg/dL.

Some experts, however, believe that LDL should be lowered even further — to less than 70 mg/dL — based on recommendations by the NCEP for people at very high risk for heart attacks and on findings from the PROVE IT trial (see "The lower the cholesterol, the better"). Talk with your doctor to determine the LDL goals that will maximize your own recovery.

Treat metabolic syndrome. Even if your LDL levels are within the target range, you may also have to use medication and make lifestyle changes to boost your healthy HDL cholesterol levels and lower harmful triglycerides — particularly if you have been diagnosed with metabolic syndrome (see "Metabolic Syndrome").

Complications and risks

Coronary artery bypass surgery is recommended only for people who can't be helped enough by heart medications or angioplasty because it is riskier than these other treatments and requires a longer recovery time. Possible complications of conventional coronary artery bypass surgery include heart attack, bleeding, and stroke. Stroke may occur if blood clots develop and travel to the brain, or if bleeding or periods of low blood pressure deprive the brain of oxygen during the surgery. About 3%–5% of people who undergo coronary artery bypass surgery have a stroke. About 5% suffer a heart attack. The risk for death from conventional coronary artery bypass surgery is about 1%–2%.

As surgical techniques improve, these numbers may go down. It is important to understand that the risk for complications or death from coronary artery bypass surgery is lowest at hospitals that perform the most bypass operations. Once again, for the best results, find an experienced heart surgeon working at a hospital with a high-volume cardiac surgery unit.

Cognitive impairment

A significant number of people experience memory problems or trouble concentrating following a coronary bypass operation, and while this may resolve with time, it is a complication that worries many patients, simply because it is so common. An often-cited study found that about half of the people who underwent coronary artery bypass surgery experienced memory impairment and cognitive decline immediately afterward. Six months later, about one in four people continued to experience cognitive decline, suggesting that the problem is temporary. Yet when the researchers examined the same people five years later, 40% showed signs of cognitive problems.

What is going on? It's not clear. Time on the heart-lung machine during traditional coronary artery bypass surgery is believed to be especially risky for the brain because blood can collect atherosclerotic particles while passing through the heart-lung machine and then deposit them in the brain.

In addition, surgeons have learned that the aorta needs to be handled especially carefully during surgery. Because people undergoing coronary artery bypass surgery have atherosclerosis in their coronary arteries, they also tend to have atherosclerosis in other blood vessels. Twisting or otherwise manipulating the aorta could cause the fragile plaques to crack and flake off into the bloodstream, contributing to strokes or other complications that could damage the memory.

Although it was hoped that off-pump coronary artery bypass surgery would reduce the likelihood of postsurgical cognitive problems, the studies have reported mixed results. Surgeons are now experimenting with and evaluating different operating-room strategies to reduce this complication, such as using special filters in the heart-lung machine to prevent atherosclerotic debris from traveling to the bloodstream, or monitoring the brain during surgery.

To further muddy the waters, a small 2002 study by neurologists who tested people both before and after coronary artery bypass surgery found that they tended to show cognitive decline even before the surgery. Because some research has suggested that some of the biological processes involved in coronary artery disease also contribute to Alzheimer's disease and other types of dementia, the researchers raised the possibility that it is the underlying disease — and not the bypass operation — that may be contributing to cognitive problems.

Researchers continue to look into this issue. But what should you do in the meantime? Talk with your surgeon ahead of time about what strategies are available to minimize the chances of memory and thinking problems. After the operation, mention any problems with attention or concentration you may be having.

Off-pump coronary artery bypass surgery

One less-invasive innovation in coronary artery bypass surgery is a procedure called off-pump bypass or beating-heart surgery because the operating team doesn't stop your heart and place you on a heart-lung machine. Instead, the surgeon uses special equipment to hold the heart steady, enabling surgeons to operate on it while it continues beating (see Figure 10).

Figure 10: Beating-heart surgery Traditional coronary artery bypass surgery requires the use of a heart-lung machine to circulate the blood while the heart is stopped. In "beating-heart surgery," also known as "off-pump" surgery, devices called stabilizers hold a portion of the heart still, allowing the surgeon to suture bypass vessels in place as the rest of the heart continues to beat. The advantages of this procedure include quicker recovery, reduced trauma to the heart and other organs, and possibly a lessening of memory loss and other neurological consequences.

Several studies have shown that off-pump coronary artery bypass surgery reduces the need for blood transfusion during the operation and results in shorter hospital stays. By avoiding the heart-lung machine, off-pump coronary artery bypass surgery was also expected to lower the rate of some complications, such as strokes and possibly memory impairment and lessened ability to concentrate. So far, though, the results of studies have been mixed. For now, in terms of effectiveness and safety, off-pump and conventional coronary artery bypass surgery seem to be equal.

Minimally invasive coronary artery bypass surgery

In minimally invasive direct coronary artery bypass surgery, the surgeon operates without making a large incision and splitting the breastbone, so recovery times are faster and risks are generally lower. This procedure can also be used either with or without the heart-lung machine. However, this procedure can only be used on people with one or two blocked arteries located at the front of the heart.

During the operation, the surgeon makes an incision of 2 1/2–4 inches on the left front side of the chest. To access the heart, the surgeon separates the pectoral muscles and removes a small portion of the front of a rib. Usually a mechanical stabilizer steadies the heart, so that it continues beating while the surgeon performs the bypass operation. However, sometimes it is better to stop the heart, using a video-assisted technique that enables the surgeon to reach more of the heart. If a heart-lung machine is used, the surgeon operates with the help of a videoscope, to see inside the chest even though it has not been opened.

Compared with conventional coronary artery bypass surgery, minimally invasive direct bypass decreases postoperative pain and reduces hospital stays to about three days on average. It is not yet known whether this procedure is as safe and effective (both in the short and long terms) as conventional coronary artery bypass surgery, because no clinical trials comparing the two techniques have yet been reported.

Last updated:	May 03, 2007