by Rosalyn Carson-DeWitt, MD
Anatomy and Physiology
Throughout the body, arteries deliver blood to the organs and tissues in order to provide them with oxygen and nutrients necessary for their functioning.
Because the heart is constantly active, it has a high requirement for oxygen. Normally, the right and left coronary arteries and their branches deliver oxygen-rich blood to the heart muscle.
Reasons for Procedure
Atherosclerosis is a condition in which fatty deposits line the inside of the arteries and interfere with blood flow. Low levels of oxygen reaching the tissues is called ischemia.
In coronary artery disease, these atherosclerotic plaques may cause ischemia of the heart muscle, or myocardial ischemia, which often leads to chest pain and can eventually damage the heart.
Pain due to ischemia of the heart muscle is referred to as angina. Angina is usually centered in the chest, but may also occur in other locations. Artherosclerosis also increases the risk of a blood clot developing in the coronary arteries, which may lead to the sudden death of the heart muscle, or a heart attack.
Tests to diagnose coronary artery disease include: an electrocardiogram, or EKG, which examines the heart's electrical activity; an exercise stress test, which is an EKG performed during exercise; a myocardial perfusion scan, which uses a radioactive substance to detect how well blood is reaching the heart muscle; an echocardiogram, which is an ultrasound of the heart that measures the function of its valves and chambers; a cardiac catheterization, which uses x-rays and a special dye to test for blockages in the coronary arteries.
In some cases, coronary artery disease may be prevented or slowed through lifestyle changes, including: weight loss, smoking cessation, a healthful, low-fat diet, prevention or treatment of high blood pressure, exercise, stress reduction.
When lifestyle changes are not sufficient, medications may help prevent or slow the progression of coronary artery disease by: lowering blood pressure, improving cholesterol levels, preventing the formation of blood clots inside narrowed coronary arteries.
Medications can also treat angina and other problems related to coronary artery disease by reducing the heart's need for oxygen.
When lifestyle changes and medications are felt to be insufficient, the following invasive procedures can be used to treat coronary artery disease: coronary angioplasty, which involves the introduction of a balloon-tipped catheter into a coronary artery to open up a blockage; coronary stenting, in which small metallic tubes are left inside blocked arteries to help keep them open after angioplasty; coronary artery bypass graft, or CABG, in which blood flow is rerouted around a coronary artery blockage through another blood vessel.
A graft involves the transfer of healthy tissue from one part of the body to another. In a coronary artery bypass graft, a healthy artery or vein is taken from elsewhere in the body and used as a detour for blood to flow around a blockage.
One or more grafts can be performed during the same operation.
Prior to your procedure, an intravenous line will be started to provide you with medications and fluid. You'll be given a general anesthetic to keep you asleep for the duration of the operation, and a breathing tube will be inserted through your mouth and into your windpipe to help you breathe.
In a traditional, "open" CABG procedure, the heart is temporarily stopped in order to keep the coronary arteries still during the surgery. In this case, a heart-lung bypass machine will be needed to deliver oxygen to your blood and to keep it circulating through your body. At the end of the procedure, your heart will be restarted and the heart-lung machine removed.
A coronary artery bypass involves two main steps. In one of the steps, your surgeon will remove, or "harvest," a blood vessel from your leg, arm, or chest to serve as the graft that will bypass the blockage in your coronary artery. As many as four blood vessels may be harvested during a CABG procedure.
There are two methods of harvesting blood vessels: the traditional open procedure requires an incision nearly as long as the vessel itself, while the minimally invasive procedure requires only tiny incisions. Once the vessel has been harvested, your surgeon will close any incisions with stitches or staples.
In the other step, another surgeon will make a vertical incision down the front of your chest and divide your breastbone. This allows the rib cage to be spread open, so that your surgeon can access your heart.
Your surgeon will then sew the harvested blood vessel, or "graft," onto the blocked artery. One end of the graft will attach upstream from the blockage and the other end downstream. This allows blood to detour around the blockage.
When all the necessary bypasses have been completed, your surgeon will wire your rib cage together and then sew or staple your chest closed.
Risks and Benefits
Possible complications of CABG include: wound infection, bleeding, heart attack, heart rhythm problems, neurological problems, including stroke or loss of memory, and/or kidney failure.
Additional complications include: depression, pneumonia, blood clots in the legs that could travel to the lungs, adverse reactions to general anesthesia.
Benefits of CABG include: improved oxygen delivery to the heart muscle, decreased angina and increased energy, ability to resume many of your normal activities.
In a CABG, or any other procedure, you and your doctor must carefully weigh the risks and benefits to determine whether it's the most appropriate treatment choice for you.
After the Procedure
After surgery, you will be transferred to the intensive care unit where: the activity of your heart and the oxygen in your blood will be closely monitored; pacing wires will control your heart rate; the breathing tube will be replaced by an oxygen mask; a bladder catheter will collect your urine; you will be given medications as needed to control your pain, heart rate and rhythm, and blood pressure.
After you are discharged, you should contact your doctor promptly if you experience: signs of infection, including fever and chills, redness, swelling, increasing pain, excessive bleeding, or discharge at the incision sites, cough, shortness of breath, chest pain, or severe nausea or vomiting, pain, burning, urgency, frequency of urination, or persistent bleeding in the urine, weight gain of more than four pounds within 1-2 days, pain and/or swelling in your feet, calves, or legs.
During your hospital stay and after you return home, you may be encouraged to attend a cardiac rehabilitation program. These programs provide structured exercise, education, and lifestyle support to help patients recover from both the physical and emotional issues that accompany heart disease and its treatment.
- Bypass surgery, Coronary artery. American Heart Association. Available at: http://www.americanheart.org/presenter.jhtml?identifier=4484. Accessed June 25, 2004.
- Coronary artery bypass graft and valve surgery. Queensland Government. Available at: http://www.health.qld.gov.au/informedconsent/ConsentForms/tpchcardiac/coronary_abgvs.pdf.Accessed June 25, 2004.
- Coronary Bypass Surgery. Mayo Clinic. Available at: http://www.mayoclinic.com/invoke.cfm?id=HB00022. Accessed June 25, 2004.
- JAMA Patient Page: Coronary Artery Bypass Grafting. Medem. Available at: http://www.medem.com/search/article_display.cfm?path=TANQUERAYM_ContentItem&mstr=/M_ContentItem/ZZZFFEJNKTD.html&soc=JAMA/Archives&srch_typ=NAV_SERCH. AccessedJune 25, 2004.
- What causes coronary artery disease? National Heart, Lung, and Blood Institute, NationalInstitutes of Health. Available at: http://www.nhlbi.nih.gov/health/dci/Diseases/Cad/CAD_Causes.html. Accessed June 25, 2004.
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