The coronary artery bypass graft (CABG) is the gold-standard surgical treatment for coronary artery disease (CAD). It is a relatively safe procedure that is performed thousands of times every year for treating CAD. CAD is characterized by the hardening and narrowing (atherosclerosis) of the coronary arteries, which supply oxygen-rich blood to the heart. If left untreated, CAD may lead to a heart attack.

During CABG, a surgeon harvests a segment of a healthy blood vessel (either an artery or  vein) from another part of the body and uses it to create a detour or bypass around the blocked portion of the coronary artery. As a result, oxygen-rich blood can flow more freely to nourish the heart muscle. Depending on the number of blocked coronary arteries, a patient may need one, two, three or more bypasses. 

For various medical reasons, only about one-tenth of CAD patients even need this type of heart surgery. Those who have the surgery need to stay in the hospital for at least three to five days afterward while recovering. After returning home, further recovery time will be necessary.

The CABG is one of the most commonly performed surgeries in the United States. According to the American Heart Association, more than 467,000 CABGs were performed in 2003. Also increasing is the age at which the procedure can be safely performed, as individuals 80 years of age and older have benefited from CABG. Although there are risks associated with any surgery, the potential life-saving benefits of a CABG usually outweigh the risks.

Coronary artery bypass surgery is often known simply as a “bypass” and is referred to as such in this article. Surgeons also perform other types of bypass surgery to treat diseases in other parts of the body, including peripheral vascular disease.

The goal of coronary artery bypass graft surgery (CABG) is not to repair or remove any blocked arteries, but to detour blood around a blockage in a coronary artery and reestablish the flow of oxygen-rich blood to the heart. To create the detour, a segment of a blood vessel is taken from another part of the body. The segment may be taken from one of the following:

• The saphenous vein from the leg is commonly used.
  
  
• The internal mammary artery from the chest is usually preferred for key artery branches because it tends to remain open longer. Some call it the internal thoracic artery.
  
  
• The radial artery from the arm and sometimes arteries from the stomach (gastroepiploic artery) may also be used as bypass grafts.

Depending on which blood vessel is used, one end is either sewn to the aorta or may remain connected to the larger artery where it originated. The other end is attached (grafted) beyond the blockage in the coronary artery. As a result, blood can flow around the blocked area, increasing the supply of oxygen and nutrients to the heart muscle.

Bypass surgery may be recommended for individuals with a history of any of the following:

• Narrowing in several coronary artery branches (common in people with diabetes)
  
  
• Severe narrowing in the left main coronary artery
  
  
• Blockage in the coronary artery or another condition that may not or has not responded to other treatments (e.g., angioplasty)
  
  
• Severe angina

Bypass surgery carries some risks, including a less than 5 percent chance of heart damage and a less than 2 percent chance of death. Studies show that women have a slightly higher risk during or immediately after bypass surgery. This may relate to the fact that women who undergo the surgery are generally older and in poorer health, and their smaller body size makes the surgery technically more difficult.  However, the overall risks are relatively low when compared to the fact that many of these bypass operations significantly lengthen and improve the quality of the patient’s life.

In some cases, the grafted arteries may also become blocked and require a second bypass surgery. Second bypass has slightly higher risks than the initial surgery, because patients are older and other, less optimal blood vessels must be used for the new grafts. However, bypassed arteries can remain functioning for many years, especially when the patient makes diet and exercise adjustments for cardiac health. Therefore, bypass surgery remains a popular choice for physicians treating severe coronary artery disease.

For several weeks before bypass surgery, patients who smoke will be advised to stop smoking. Many surgeons also advise their patients to stop taking aspirin to minimize the risks of excessive bleeding during and immediately after surgery. Patients will also be asked not to eat or drink anything after midnight before surgery. Certain medications, especially those that affect blood clotting, may be reduced or stopped. Patients should discuss their medication schedules with their physician.

The patient is usually admitted the morning of surgery. A few days before surgery, the patient undergoes a number of tests, which include an x-ray, blood tests, urinalysis and an electrocardiogram (EKG). The patient’s blood is typed and cross–matched with units of donor blood, according to the surgeon’s wishes. Blood transfusions may not be needed. Patients should know, however, that blood banks test blood to screen donor blood for most major diseases, such as hepatitis or AIDS.

The patient will be given specific pre-operative medications and is then prepared for surgery. The chest, groin and leg areas are shaved, and a bacteria-killing (bactericidal) solution is applied to the operative site and surrounding area. The patient is then sedated with medication given through an intravenous (I.V.) line in the arm or hand. As soon as the patient is asleep, an anesthetic inhalation gas (general anesthesia) is continuously administered through an endotracheal tube (breathing tube) and constantly monitored by the anesthesiologist.

After the patient is asleep, a device called a Swan-Ganz catheter is often inserted through a needle stick into the jugular vein (in the neck) and threaded to the pulmonary artery (which goes from the heart to the lungs). The catheter is used to measure heart function, measure the pressures in both the heart and lungs, and to give any necessary medications. The endotracheal tube, which was inserted into the mouth and down the windpipe (trachea), is used to maintain an airway. A urinary catheter is also inserted and connected to a collection bag to measure the patient’s urine output. 

An incision is then made in the chest, through the breastbone (sternum), and the two halves of the breastbone are divided (median sternotomy). A medical device called a retractor is used to pull back the two halves of the breastbone to give the surgeon plenty of room to work. The ribs are not divided, reducing discomfort during recovery. 

The functions of the heart, including blood flow and oxygenation, are rerouted through a heart-lung machine. While the machine takes care of the heart’s functions, the heartbeat can be carefully stopped by administering a cardioplegic solution. In total, the heart will remain stopped for about 30 to 90 minutes during the four to five hours (on average) of surgery.

Before the heart is stopped, the blood vessel(s) to be used as grafts are removed from their source location. If they are located in the chest, one end of the blood vessel(s) may remain connected to the larger artery it originated from, or it will be sewn to the aorta, depending on which blood vessel is used for the graft. The other end is sewn into place below the blockage in the coronary artery. After the graft(s) are completed, and blood is successfully flowing around the blockage, the heart is restarted and the patient is removed from the heart-lung machine. Finally, when normal blood flow and heartbeat are re-established, the surgical site is carefully closed layer by layer. The sternum is usually closed with wire and the surface incision is closed with staples or sutures, depending on the surgeon’s preference.

Although coronary bypass is a relatively safe surgery with an extensive history in patients, researchers are still looking for ways to improve it. For instance, studies are underway to investigate new ways of grafting blood vessels. One method involves a “sewing” device consisting of two sets of hooks. One set holds the graft; the other makes the attachment to the aorta. In the small group of individuals having undergone the procedure, the graft was connected in less than two minutes (versus up to seven minutes with current methods). Researchers also noted a better quality of connection. Moreover, it resulted in less time required on the heart-lung machine.

Another technique, still in the animal testing stages, involves connecting grafts with an adhesive. Researchers think that either procedure may someday find use in minimally invasive bypass surgery and may make the heart-lung machine unnecessary in standard coronary bypass surgery. 

Coronary artery bypass surgery can also be performed in conjunction with other cardiac surgical procedures to treat other conditions that may have occured at the same time (e.g., stenosis, leakage of cardiac valves). A transesophageal echocardiogram is often required during surgery to detect these abnormalities and document the success of the surgery.

After surgery, the patient is moved to a hospital bed in the cardiac surgical intensive care unit. Heart rate and blood pressure monitoring devices continuously monitor the patient for 12 to 24 hours. Family will be able to visit periodically. Medications that regulate circulation and blood pressure may be administered through the intravenous tube. A breathing tube (endotracheal tube) will remain in place until the physicians are confident that the patient is awake and ready to breathe comfortably without assistance. 

The patient may feel groggy and disoriented, and sites of incisions – both the chest and the leg, if a segment of blood vessel was taken from the leg – may be sore. Painkillers are given as necessary.

Patients usually stay in the hospital at least three to five days and sometimes longer. During this time, tests will be conducted to assess and monitor the patient’s condition. After release from the hospital, the patient may experience side effects, such as:

Many of these side effects usually disappear over the course of four to six weeks, although a full recovery may take a few months or more. When the patient is ready, he or she may be enrolled in a physician-supervised program of cardiac rehabilitation. This program teaches stress management techniques and other important lessons (e.g., about diet and exercise) and helps people to rebuild their strength and confidence.

A successful surgery results in a dramatic increase in blood flow to the heart muscle. This increase in blood flow, in turn, reduces the pain, pressure or discomfort (angina) associated with cardiac ischemia. Abnormal heart rhythms (arrhythmias) may develop just after the surgery and may last three to four days, but these abnormal heart rhythms are usually only temporary. In addition, the chest and leg area where incisions were made will likely be slightly sore for at least a few weeks. However, severe pain should be reported to a physician.

 Complications that may arise from bypass surgery include:

Most of these complications are short-term and are not serious, though advanced age and poor overall health may increase their risk and severity. More serious complications that may arise, usually due to the use of the heart-lung machine, include kidney failure, heart attack, stroke or even death. These risks are higher for older patients, people with diabetes and patients with other major health problems. However, it's also important to note that in recent years, the risk of serious complications due to cardiopulmonary bypass has been dramatically reduced due to improved surgical techniques. In one study, researchers found that the rate of serious complications fell by half in the period from the early 1980s to the mid 1990s. In addition, physicians have a number of tools at their disposal to further reduce the risk of post-operative complications. This includes the use of medications, such as aspirin and beta blockers, and very strict blood sugar control.  

One area of complication occurs when grafted arteries become blocked over time and a patient needs a second bypass surgery. This procedure presents greater risks for several reasons. The patient is older and their heart disease has usually worsened. The blood vessels used as grafts in the first surgery are not available to use for the second surgery. In addition, there may be adhesions around the original grafts that make the second surgery more difficult.  Patients should discuss all additional risks with their physician.

Postoperative bypass patients can improve their health and lessen their likelihood of further cardiac disease. Positive lifestyle changes can help. These include:

Following the surgery, and for the first few months afterward, the bypass patient is encouraged to slowly resume an enjoyable and active life, while minimizing the risks associated with overexertion. At first, relaxation is extremely important. Patients will want to make sure that the physical process of healing goes smoothly. Patients should restrict certain activities, such as lifting objects over 20 pounds, driving, and exposing themselves to highly stressful or strenuous situations. When it is comfortable to do so, light aerobic exercise – particularly walking – is the next step to regaining strength and maintaining a healthy heart. Patients who have jobs that do not require heavy manual labor (e.g., a desk job) may be able to return to work in about four to six weeks.

Even with these and other limitations as instructed by the physician, the most important factor for living well is preventive care. Spending time with family and friends will help bypass patients to stay active. Eventually, many people can return to their places of employment or find another type of work or volunteer activity that keeps them both fulfilled and medically safe.

There are a number of other procedures or variations of the bypass that are being used or considered as alternatives. In general, two main alternatives have emerged. The first is known as minimally invasive direct coronary artery bypass surgery, or MIDCAB for short. MIDCAB surgery is performed through smaller incisions, often in the side of the chest, rather than the large, frontal sternotomy. This is sometimes referred to as “keyhole” surgery. In some centers, MIDCAB surgeries are performed with the use of advanced robots, although this remains very limited.

The second major alternative to conventional bypass surgery is known an off-pump coronary artery bypass surgery, or OPCAB. During this procedure, the surgeon operates on a beating heart. The heart-lung machine is not used, and the heart is not stopped. Instead, the surgeon uses special stabilizers and other techniques to isolate the coronary arteries and operate on them. The major advantage to this surgery is avoiding any potential complications involved with the bypass machine.

There can be overlap between these alternatives and the more conventional bypass surgery and therapy. For instance, a MIDCAB surgery can be performed without using the heart-lung machine, so it is also off-pump. Similarly, an off-pump surgery may be performed using a sternotomy, so it is comparable in recovery time to a conventional bypass surgery.

There are relative advantages and disadvantages to each of the newer procedures. However, MIDCAB surgery faces greater obstacles to widespread acceptance than OPCAB. Because the incisions are smaller, surgeons are limited in their ability to reach certain areas of the heart during MIDCAB surgery. Thus, studies have looked at combining MIDCAB on one coronary artery (e.g. the left anterior descending coronary artery) with conventional balloon angioplasty on other coronary arteries. At this time, however, MIDCAB remains significantly more expensive and technically demanding than conventional and OPCAB surgeries and there are no long-term studies on its results.

Minimally invasive techniques have also migrated to the harvesting of veins for the bypass grafts. In this procedure, a surgeon uses a special device called an endoscope to remove the leg vein (the saphenous vein) through small incisions. This is called endoscopic vein harvesting. It may be used with either conventional bypass surgery, or it may be used with OPCAB in a series of procedures known as off-pump coronary revascularization with endoscopic saphenous vein harvesting (OPCRES). 

With advancing technology and experience, OPCAB- with or without endoscopic vein harvesting – has become relatively widespread. The Society of Thoracic Surgeons estimated that in 2001, “beating heart” surgeries accounted for 25 percent of bypass operations. Initial studies show that OPCAB has approximately the same results as conventional bypass surgery, and because the surgeon is usually operating in a wide field through a sternotomy, it can be used for multi-vessel disease.

A number of even less invasive techniques may be used to treat a blocked artery. For example, many patients are recommended for balloon angioplasty with stenting. This technique uses an inflatable balloon that crushes plaque against the wall of the artery to improve blood flow. This procedure is usually followed by placement of a coronary stent – a wire mesh metal tube – into the artery to hold it open afterward. 

Catheter-based techniques such as this are less invasive and less expensive than standard bypass surgery. On the other hand, they may need to be repeated sooner than would a bypass. Many first-time bypasses – between 70 and 90 percent, depending on the blood vessel used for the graft – remain open for 5 to 10 years or longer, whereas about 20 percent of catheter-based procedures that use a balloon and stent combination may need to be repeated within the year. Newer stents, called drug-eluting stents, are coated with special medications that further reduce the closure rate, to less than 10 percent. However, newer research has called into question the long-term performance of some drug-eluting stents, and researchers are currently reevaluating the decision to use a traditional or drug-eluting stent.

At least in some patients, it appears that drug-eluting stents may increase the long-term risk of blood clots, with possibly devastating consequences. One study indicated that patients who stop taking their prescribed medicines early are at a higher risk of blood clots than patients who continued to follow their prescriptions. Nevertheless, as a result of advances in stent design, the number of stent procedures has increased, whereas the number of bypass operations has decreased over the past 10 years. 

Some researchers are hoping that therapeutic angiogenesis may one day offer the benefits of a bypass with still less invasiveness. Therapeutic angiogenesis is an experimental treatment for angina, which is a common symptom of the cardiac ischemia that often results from coronary artery disease. Angina is a chest pain, pressure or discomfort that often results from usually temporary episodes of cardiac ischemia – an episode in which the heart does not get enough oxygen–rich blood. In response to this situation, the body often forms new blood vessels (collaterals) that bring more oxygen-rich blood to the heart, relieving cardiac ischemia and angina. This natural process is called angiogenesis. Researchers are attempting to medically coax the body to produce its own natural response of angiogenesis to lessen the need for bypass surgery.

Preparing questions in advance may help patients have more meaningful discussions with their physicians about their conditions. Patients may wish to ask their doctors the following questions related to coronary artery bypass graft surgery (CABG):

1. Why do I need bypass surgery instead of angioplasty?
   
   
2. How many CABG surgeries have you performed?
   
   
3. What complications will my other medical conditions present for surgery?
   
   
4. Will I have to take any medications regularly after surgery?
   
   
5. If you cannot access the blocked arteries with angioplasty, how do you know you can do so surgically?
   
   
6. What type of surgical procedure do you recommend?
   
   
7. Will this surgery involve a heart-lung machine or not?
   
   
8. How soon after a heart attack can CABG surgery be performed?
   
   
9. How does my diabetes complicate bypass surgery?
   
   
10. Do you always recommend surgery for patients with my background and symptoms?
    
    
11. I had bypass surgery 15 years ago. How will it be different this time?
    
    
12. If I have bypass now, will I have to have surgery or angioplasty again?
    
    
13. Will lifestyle changes after my surgery help lessen the chance of another bypass surgery?