Risks of coronary artery bypass graft surgery

Prior to the beginning of the procedure, your surgeon will discuss with you the risks and potential complications of coronary artery bypass graft (CABG) surgery. Make certain that you understand these risks before you consent to the procedure.

Your risks can be different than the risks for somebody else, based on your current health status. For otherwise healthy individuals, the CABG procedure is a reasonably common and uncomplicated procedure. However, certain risks are associated with all invasive surgeries, including CABG surgery, and are higher if you have other medical conditions.

Understanding the risks

Your surgeon will discuss these risks during your first visit, well before your CABG takes place. Your surgeon will also describe specific complications that might arise. He or she will review this information with you again on the day of your CABG procedure. If you have any questions at either of these meetings or while you are at home resting before the procedure, make sure to ask your surgeon for clarification.

To make sure that you understand these risks, your surgeon will probably ask you to sign a waiver (an informed consent form) that lists these potential risks and complications in writing.


Because bacteria are naturally present in the air and on your skin, you will always be at risk of infection whenever internal organs or tissues are exposed to the air. That is why even small cuts can sometimes become red and sore.

Despite the fact that sterilized equipment will be used during your CABG procedure, there is a risk of developing an infection in any of your wounds or incisions (namely, on your chest and legs or arms). You are also susceptible to pneumonia.

Other medical conditions and risk of infection

Your chances of developing an infection increase significantly if you have several other medical conditions at the time you have CABG. In general, these conditions weaken your immune system, which fights off infections in your body. Examples of such conditions are:

  • Severe lung disease. This underlying condition weakens your lungs, making them more susceptible to pneumonia.
  • AIDS. HIV and AIDS decrease the strength of your immune system.
  • Old age. It has long been observed that your immune system deteriorates with age.
  • Radiation to the chest. Radiation not only weakens your immune system but also damages muscle, bone, and tissue within the chest, making it more open to infection.
  • Reoperation. Second and third surgeries often aggravate the same sets of tissues, leaving them weakened and more prone to infection.
  • Diabetes. Poorly controlled diabetes can increase the risk of infection.

Superficial bleeding

After surgery, most people bleed from their incisions the same way they would from any cut. Since your chest incision from a CABG procedure is large, you are likely to have quite a bit of bleeding there, as well as some bleeding from your arm or leg incisions.

Internal bleeding

Excessive internal bleeding is a relatively uncommon complication of CABG. There are two types of internal blood loss:

  • A hematoma, or bruise, is a small loss of blood that tends to pool near the skin. A hematoma happens when there is a tear in a small blood vessel. It can be self-contained and not dangerous, or it could be more severe and require surgery.
  • A hemorrhage is significant blood loss that occurs when a large blood vessel like the aorta (the main artery carrying blood out of your heart) tears. This is a very serious problem that can happen either during or after surgery and requires emergency attention.

Blood flow problems

  • Red blood cells. Red blood cells carry oxygen to all parts of your body. Red blood cells passing through the heart-lung bypass machine during CABG surgery can be damaged or deformed, reducing the number of normal red blood cells available for the delivery of oxygen to the body.
  • Plaque rupture. Your surgeon will manipulate your aorta or coronary arteries during the CABG procedure. Sometimes this causes a small piece of the plaque inside your aorta or arteries to break off and move through your bloodstream. The plaque fragment eventually lodges in a smaller blood vessel in another part of your body, possibly blocking blood flow and oxygen.
  • Blood clots. Blood clots can also develop during CABG surgery. These clots form because blood is circulated though your body using a bypass machine while you're lying still for hours of surgery. Your circulation slows down while you are on bypass, allowing blood cells to stick together. A blood clot can also get stuck in a smaller blood vessel and result in a blockage. Such an obstruction can occur in any part of your body.
    • Brain: If the obstruction occurs in a blood vessel supplying blood to the brain, it results in a stroke. Between 10% and 30% of people have persistent cognitive impairment 3 to 6 months after CABG surgery, probably due to multiple microscopic strokes that occur during surgery.1
    • Organs: If a blood vessel supplying blood to one of your organs becomes obstructed, serious problems can occur. For example, blocked blood flow to a kidney can cause high blood pressure (renal hypertension) and kidney damage.
    • Extremities: An obstruction can block blood flow to one of your extremities, causing damage to fingertips or toes.

Serious complications that can occur during a CABG procedure

During CABG surgery, your heart is stopped, surgery is done to form bypasses, and then your heart is started again. These steps can cause problems for your heart, including:

  • Heart attack. If a piece of loose plaque or a blood clot blocks the blood flow in one of your coronary arteries, it will cause a heart attack. This is a severe complication that requires immediate intervention.
  • Irregular heart rhythms. Your heart is stopped during a standard CABG surgery. When it is restarted, it may develop an abnormal rhythm. Most often, the abnormal rhythm is postoperative atrial fibrillation and will resolve with medications and time.

Given the degree of invasiveness, CABG surgery is a relatively safe operation. However, death can still occur during CABG surgery, typically as a result of a heart attack or some other cardiac complication.

In rare instances, an allergy to a medication or an inadvertent tearing of the aorta during surgery may also cause death.

Research suggests that patients with the highest risk of dying during CABG surgery are those with heart failure. Heart failure is a condition where the left ventricle (the heart chamber that pumps blood out to the body) is already functioning poorly before the surgery.

Other factors that increase your risk of death during and after a CABG operation are:

  • The presence of other medical problems such as lung disease, liver failure, or kidney failure.
  • Old age. As the body ages, it is less able to prevent potentially life-threatening infections after surgery.
  • Surgical inexperience. An experienced surgical team may be better at dealing with unexpected complications during surgery.

Final thoughts

Overall, the risks associated with CABG surgery are relatively small. Persons with other medical conditions, particularly heart and lung conditions, face a greater risk of death and complications during bypass surgery. Regardless of your health status, you should educate yourself about the potential complications of CABG surgery and talk with your doctors about your personal risk.


  1. Sila CA, Furlan AJ (2002). Cerebrovascular disease. In EJ Topol et al., eds., Textbook of Cardiovascular Medicine, 2nd ed., pp. 2083–2108. Philadelphia: Lippincott Williams and Wilkins.

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