Patient information: Coronary artery bypass graft surgery

BYPASS SURGERY OVERVIEW

In coronary heart disease (CHD), the coronary arteries become clogged with calcium and fatty deposits. The deposits, called plaques, narrow the arteries that carry blood to the heart muscle (figure 1). Blood supplies the heart muscle with oxygen and sources of energy; ischemia (a reduction in blood flow and oxygen) can produce symptoms of pain in the chest (angina pectoris). In more severe cases, heart attack (myocardial infarction), heart failure, or rhythm abnormalities can cause sudden cardiac death.

Coronary artery bypass graft surgery, or CABG (pronounced "cabbage"), is a procedure that uses your own veins (usually from the legs) or arteries to bypass narrowed areas and restore blood flow to heart muscle. Thus, bypass surgery can effectively relieve chest pain for most patients, and can prolong life for those with certain patterns of severe coronary heart disease.

The final decision regarding the best choice of treatment depends upon several factors, including the benefit versus risk of surgery, the severity of your symptoms and cardiac disease, and your underlying medical problems. You should discuss the details of your case with your healthcare provider.

IS BYPASS SURGERY RIGHT FOR ME?

Surgical treatment may be recommended for different situations:

Stable angina — Angina (chest pain) is considered stable when its frequency, severity, duration, and precipitating factors are not changing. Patients with stable angina may require CABG if there are persistent and intolerable symptoms despite adequate medical treatment, specific patterns of arterial narrowing in several vessels, or patients with a high risk of heart attack and death.

Extensive disease — Patients with extensive CHD, including narrowing of the left main coronary artery, multiple narrowed coronary arteries, and poor pumping function of their left ventricle (lower heart chamber) generally live longer when they undergo CABG as compared to patients who have medical or less invasive (balloon angioplasty or stent) treatment.

Future risk of cardiac event — Patients who are identified as having a high risk for a future cardiac event, based on an exercise test. The test may show changes in the EKG, poor exercise capacity, failure to raise blood pressure, or severely limited blood flow to multiple areas of the heart. Blood flow is measured with a myocardial perfusion scan or echocardiogram obtained immediately after exercise.

Unstable angina — Patients who develop unstable angina may be candidates for CABG or angioplasty (stent therapy). Angina is considered unstable if it becomes more frequent, occurs with less exertion or at rest, is more severe, lasts longer, or fails to respond to appropriate medication.

After myocardial infarction — Patients who have had a myocardial infarction (heart attack) may undergo CABG if their blood vessels cannot be opened with balloon angioplasty (for more information on angioplasty, (see "Patient information: Angina treatment — medical versus interventional therapy" section on Interventional treatment.) .

BYPASS SURGERY PROCEDURE

With CABG surgery, a vein or artery taken from elsewhere in the body is grafted from the aorta (the major blood vessel exiting the heart) onto the coronary artery, beyond the narrowed segment. This avoids (bypasses) the diseased section and restores blood flow to the area of the heart muscle supplied by that artery. Multiple grafts may be used if more than one coronary artery is diseased.

Choice of graft — Generally, blood vessels can be obtained from four areas of the body: leg, chest, arm, and abdomen.

• Saphenous veins are taken from the leg (calf or thigh). Historically, the saphenous vein was the graft of choice. However, narrowing (stenosis) of the vein graft, due to changes that are similar to those of a coronary artery, is a major problem with saphenous vein grafts, causing them to deteriorate within five to seven years in approximately 50 percent of patients. A number of factors may predispose to saphenous vein graft disease, including smoking, hypertension, lipid abnormalities, and diabetes.
• Internal mammary arteries (also called or internal thoracic arteries) are on the left and right side of the breast bone, at the center of the front part of the chest. Unlike vein or radial artery grafts, internal mammary grafts are not fully removed from their original position. These grafts remain connected to their natural site of origin, and only one end is separated from the chest wall. This end is then attached to one of the coronary arteries.

Arterial grafts rarely develop stenosis and have an improved long-term survival compared to vein grafts. In addition, patients with arterial grafts tend to have better survival, fewer reoperations, a lower rate of myocardial infarction (MI), and less recurrent angina, as compared to vein grafts. Fortunately, the left internal mammary artery, or LIMA, runs close to the most important coronary artery, the left anterior descending coronary artery, or LAD. Thus, the most important coronary artery is often bypassed with the most effective type of graft.

• Radial arteries are taken from the inner forearm. The long-term outcome with these arteries is also excellent and almost equivalent to that of the internal mammary artery. There are usually only minimal changes in hand function after removal of the radial artery for CABG, manifest as a small amount of forearm numbness and tingling, but generally no change in motor function or tolerance to temperature or pain. In the majority of these patients, the symptoms are self-limited.
• The gastroepiploic artery, which comes from the stomach, is another option for grafting. It is currently used rarely, although results with this artery are encouraging.

The surgery — Conventional CABG is performed while the patient is under general anesthesia (completely asleep with medication). The surgery generally takes three to six hours. The surgeon makes an incision in the breastbone (sternum), called a median sternotomy, to open the chest and gain access to the heart. If the internal mammary artery is being used, it is separated from the chest wall; if a vein or radial artery is being used, it is removed from the leg or arm.

Attaching the bypass vessel to the coronary artery requires the heart to be temporarily stopped using chemicals or cold (hypothermia) so that the surgeon can sew on the grafts.

While the heart is stopped, blood circulation is maintained with a heart-lung machine, or cardiopulmonary bypass machine. This functions like the heart and lungs, circulating blood and providing oxygen to the body. Fluids, nutrients, and medications may be added to the blood while it passes through the cardiopulmonary bypass machine.

The surgeon sews one end of the graft onto the aorta and the other end to a part of the coronary artery below the narrowing, hence bypassing the diseased area.

New procedures — Several new surgical approaches are now being developed that may reduce the discomforts and risks associated with traditional bypass surgery. Known as "minimally invasive bypass surgery" and "off-pump surgery," these approaches use a small chest incision and are performed on the heart while it is still beating. These techniques have become increasingly popular but are not appropriate for all bypass situations. Long-term outcomes seem to be comparable to the standard CABG operation and generally involve a shorter stay in the hospital.

BYPASS SURGERY RECOVERY

Immediately after surgery, the patient spends one to two days in an intensive care unit. Family members can visit periodically during this time. A number of systems are used to monitor the patient's heart rate and rhythm, blood pressure, temperature, and breathing rate; monitoring is gradually discontinued as the person recovers.

• The breathing tube that was placed in the airway before surgery is removed as soon as the patient is awake and able to breathe on their own. Most people awaken within a few hours after surgery. It is common to feel groggy and disoriented during this time.
• A thin, flexible tube (catheter) is usually placed in the bladder before surgery begins. The catheter is needed to collect and measure urine. Once the person is able to get up and go to the bathroom, the catheter is removed.
• Fluids, medications, and sometimes blood transfusions are given before, during, and after the surgery through an intravenous (IV) line. When the person is able to eat and drink and no longer requires IV medications, the line is removed.
• Tubes are placed inside the chest to drain fluids that accumulate around the heart after surgery. These are usually removed within one to three days after surgery.
• The incision in the chest is usually sore, with the most discomfort in the first 48 to 72 hours after surgery. Pain medications are usually given to relieve discomfort.

When continuous monitoring is no longer required, usually after 12 to 24 hours, most patients are moved to a step-down or transitional care unit. Most people can sit in a chair the day after surgery. The person is encouraged to start walking within one to two days after surgery.

• Many people have a poor appetite for several weeks after surgery. This is normal and expected. Talk to a doctor or nurse if there are concerns about appetite.
• Constipation is also common during this time, probably due to decreased activity and food intake and use of pain medications. Medications to relieve constipation may be recommended. (See "Patient information: Constipation in adults".)

• People who have a graft harvested from the leg sometimes notice swelling in this leg after surgery. Elevating the leg and wearing compression stockings can help to reduce swelling.
• It is common to have difficulty sleeping after bypass surgery, especially while in the hospital. This usually improves after discharge from the hospital.
• Approximately 20 to 40 percent of people become depressed after CABG. Signs of depression include sadness for most of the day, diminished pleasure or interest in almost all activities, insomnia or excessive sleep, or feelings of worthlessness or guilt. Depression can interfere with recovery and increase the risk of heart problems in the future. Anyone who notes signs of depression that last for more than two weeks should speak to their healthcare provider about treatment options. (See "Patient information: Depression in adults".)

Most people recover in the hospital for four to five days after surgery. However, hospitalization may be longer, depending upon the an individual's rate of recovery and any complications that develop.

People who do not have complications or a prolonged hospital stay are usually able to return to desk work within four to six weeks. People who have a physically demanding job often need more time to recover. Complete recovery from surgery often takes two to three months. Care at home after surgery is discussed in a separate topic review (see "Patient information: Recovery after coronary artery bypass graft surgery (CABG)".

BYPASS SURGERY COMPLICATIONS

There are a number of complications that can occur after CABG. The major complications include bleeding that may require a return to the operating room, heart attack, heart failure, arrhythmia, stroke, changes in cognitive function, pulmonary problems, wound infection, renal failure, and death.

Postoperative complications may be related to the body's response to artificial blood circulation and gas exchange through the cardiopulmonary bypass apparatus.

Cardiac complications — Many complications affect the heart directly.

• Two to 4 percent of patients experience a heart attack after surgery. This occurs less frequently in patients who are low risk as compared to patients who are high risk, undergoing repeat CABG, or CABG combined with other cardiac surgery. Generally post-operative heart attacks are small to moderate in size.
• Low cardiac output (when a reduced volume of blood is pumped out of the heart to the body) can occur during or after surgery. This is often temporary and responds to intravenous fluids and/or a brief period of therapy to improve heart function. Therapy may include medications or a special mechanical device that can augment the heart's ability to contract (intraaortic balloon pump or left ventricular assist device).
• Tachyarrhythmias, temporary rapid and/or irregular heart rhythms, may occur after CABG.

Atrial fibrillation, an abnormal rhythm of the heart, occurs in up to 40 percent of cases but can be controlled with medications. This rhythm disturbance may cause a blood clot to develop within the heart. If this blood clot becomes dislodged, it can travel to another organ in the body, such as the brain, resulting in a stroke. Atrial fibrillation after CABG is usually temporary; if persistent, patients may require treatment. (See "Patient information: Atrial fibrillation".)

Sustained ventricular tachycardia (a rapid and regular heart beat) or ventricular fibrillation (a rapid, chaotic, and ineffective heart beat) occurs in approximately 2 to 3 percent of patients, usually within four days of surgery. An automatic internal defibrillator may be needed for selected patients. (See "Patient information: Implantable cardioverter-defibrillators".)

Postoperative bradyarrhythmias cause the heart to beats too slow and requires placement of a permanent pacemaker in 0.8 to 4 percent of patients. (See "Patient information: Pacemakers".)

• Pericarditis is an inflammation of the pericardium, the sac that surrounds the heart. Sometimes pericarditis is accompanied by pericardial effusion, in which the pericardial sac fills up with fluid. If a large amount of fluid accumulates in the pericardium, it may push on and squeeze or constrict the heart, called cardiac tamponade.

Pericarditis often causes chest pain, which generally occurs a few days to several weeks after surgery. Pericardial effusions are usually small and resolve without treatment. If the effusion is large, urgent treatment or reoperation may be needed.

Bleeding — Approximately 30 percent of patients require a blood transfusion after CABG. Patients with heavy bleeding that requires reoperation often need multiple blood transfusions and stay longer in the intensive care unit and hospital. Only about 2 percent of people require surgery to stop excessive bleeding.

One factor that increases the risk of postoperative bleeding is exposure to aspirin in the week before surgery. However, some patients should continue aspirin therapy before CABG to maintain its beneficial effect. Plavix® (clopidogrel) and ibuprofen are generally discontinued for several days prior to coronary surgery. Patients taking warfarin (Coumadin®) should speak with their surgeon about how and when to stop it before surgery. (See "Patient information: Warfarin (Coumadin®)".)

Neurologic complications — Neurologic complications include stroke, postoperative delirium, short-term and long-term cognitive changes, and depression. The incidence of neurologic problems following CABG is approximately 2 to 4 percent; older patients and women are affected more frequently.

Infection — The surgical sites involved in CABG can become infected after the surgery.

Sternal wound — Infection of the chest incision (called the sternal wound) occurs in approximately 1 percent of patients. It usually develops by 7 to 9 days after surgery. Diabetes mellitus, obesity, and the use of both left and right internal mammary arteries increase the risk of sternal wound infection. Women with a history of breast cancer are at especially high risk, possibly related to therapies used during breast cancer treatment.

Leg wounds — Leg wounds develop complications after saphenous vein graft harvesting in approximately 5 percent of patients. The most common complications include dermatitis (inflammation of the skin), cellulitis (a bacterial infection of the skin), nerve damage, and non-healing ulcers; most are minor and do not require surgical intervention.

Renal failure — A temporary decrease in kidney function occurs in approximately 5 to 10 percent of patients undergoing CABG.

Other complications — A number of other complications may occur as well.

• Pleural effusions — Pleural effusions are collections of fluid in the membranes surrounding the lungs. These are common after CABG, occurring in up to 90 percent of patients. They are usually small and do not require treatment.
• Phrenic nerve damage — The phrenic nerve, the nerve that controls the diaphragm, is damaged during CABG in less than 1 percent of patients. Damage can cause diaphragm dysfunction or paralysis. Most people recover fully within one year.
• Intercostal nerve damage — The intercostal nerves are connected to the thorax and abdomen. Harvesting the internal mammary artery can injure these nerves. Symptoms of nerve damage include numbness, tenderness, or burning discomfort over the sternum and left anterolateral chest wall. Pain usually subsides by four months.
• Aortic dissection — Aortic dissection, a disorder in which the layers of tissue that make up the aorta split apart, can occur after CABG. People who are elderly, have longstanding high blood pressure, severely narrowed coronary arteries, or widening of the aorta are at greater risk.
• Thrombocytopenia — Heparin is given during CABG to prevent the blood from clotting during and after the procedure. In some cases, heparin can cause a decrease in the number of platelets in the blood (called thrombocytopenia), which can decrease clotting ability and increase the risk of bleeding. If needed, other medications may be used to induce anticoagulation without producing thrombocytopenia.

LONG-TERM OUTCOME

As mentioned above, patients with symptomatic angina who undergo CABG can have greatly improved outcomes. As an example, in the Coronary Artery Surgery Study (CASS) of 8221 patients undergoing CABG, 56 percent were alive at 15 years. Among those 65 and 75 years of age at the time of surgery, 15 year survival was 54 and 33 percent, which was higher than a similar age group in the United States who did not have CABG.

There are a number of factors that influence the long-term outcome of a patient that has undergone CABG. One of these is how patent, or open, the graft remains over time. If the grafts do not remain open, an angioplasty or another operation may be needed. The choice of graft, as discussed above, can greatly influence the need for reoperation.

Angina after surgery — About 95 percent of people who have narrowing of several arteries have improvement or complete relief of their angina immediately after surgery. About 85 to 90 percent of people remain angina-free at one to three years after surgery, and about 75 percent of people remain angina-free or free of major coronary events at five years after surgery.

Reasons for recurrence of angina include

• Narrowing that develops in the graft used for the bypass or
• Progression of disease in the bypassed or non-bypassed vessels.

The recurrence of angina is less frequently seen when the vessel used for the bypass is an artery as compared to a vein. By 10 years, 90 percent of arterial grafts are still open; in contrast, about one-half of all vein grafts become narrowed or occluded at 10 years after bypass surgery, and by 15 years, about 85 percent of vein grafts become narrowed or occluded. These late events, which are often associated with recurrence of symptoms, usually require a second revascularization procedure, most often done with angioplasty or stent placement, and less often with a repeat surgical bypass.

CARE AFTER BYPASS SURGERY

Cardiac recovery and care is discussed in detail in a separate topic review. (See "Patient information: Recovery after coronary artery bypass graft surgery (CABG)".)

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Angina treatment — medical versus interventional therapy
Patient information: Constipation in adults
Patient information: Depression in adults
Patient information: Recovery after coronary artery bypass graft surgery (CABG)
Patient information: Atrial fibrillation
Patient information: Implantable cardioverter-defibrillators
Patient information: Pacemakers
Patient information: Warfarin (Coumadin®)

Professional Level Information:
Bypass surgery versus percutaneous intervention in the management of stable angina pectoris: Clinical trials
Bypass surgery versus percutaneous intervention in the management of stable angina pectoris: Recommendations
Coronary artery bypass grafting in patients with cerebrovascular disease
Early cardiac complications of coronary artery bypass graft surgery
Early noncardiac complications of coronary artery bypass graft surgery
Long-term outcome after coronary artery bypass graft surgery
Medical versus interventional therapy in the management of stable angina pectoris
Minimally invasive aortic and mitral valve surgery
Minimally invasive coronary artery bypass graft surgery: Clinical efficacy of beating heart surgery
Neurologic complications of cardiac surgery
Postoperative mediastinitis after cardiac surgery

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• National Heart, Lung, and Blood Institute

      (www.nhlbi.nih.gov/)

• American Heart Association

      (www.americanheart.org)

• Society of Thoracic Surgeons

      (www.sts.org)

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