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Coronary artery bypass surgery, also coronary artery bypass graft surgery and heart bypass (colloquial), is a surgical procedure performed on patients with coronary artery disease (see atherosclerosis) for the relief of angina and possible improved heart muscle function. Veins or arteries from elsewhere in the patient's body are grafted from the aorta to the coronary arteries, bypassing coronary artery narrowings caused by atherosclerosis and improve the blood supply to the myocardium (heart muscle).
Terminology There are many variations on terminology, in which one or more of 'artery', 'bypass' or 'graft' is left out. The acronym for this type of surgery might therefore be CABG (pronounced 'cabbage'), CABGs (pronounced 'cabbages') or CAGS (pronounced phonetically). Prognosis Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10-15 years. In general, CABG improves the chances of survival of patients who are at high risk (meaning those presenting with angina pain shown to be due to ischemic heart disease), but statistically after about 5 years the difference in survival rate between those who have had surgery and those treated by drug therapy diminishes. Age at the time of CABG is critical to the prognosis, younger patients with no complicating diseases have a high probability of greater longevity. The older patient can usually be expected to suffer further blockage of the coronary arteries. Complications Procedure (Simplified) 1) An artery may be detached from the chest wall and the open end attached to the coronary artery below the blocked area. 2) A piece of a long vein in the leg may be taken. One end is sewn onto the large artery leaving the heart -- the aorta. The other end of the vein is attached or "grafted" to the coronary artery below the blocked area. Either way, blood can use this new path to flow freely to the heart muscle. Conduits used for bypass Typically, the left internal thoracic artery (LITA) (previously referred to as left internal mammary artery or LIMA) and right internal thoracic artery are used for bypass. If additional bypasses are required the great saphenous vein from the leg or the radial artery from the forearm are frequently used. Veins that are used either have their valves removed or are turned around so that the valves in them do not occlude blood flow in the graft. LITA grafts are longer-lasting than vein grafts, both because the artery is more robust than a vein and because, being already connected to the arterial tree, the LITA need only be grafted at one end. The LITA is usually grafted to the left anterior descending coronary artery (LAD) because of it superior long-term patency when compared to saphenous vein grafts. The LAD supplies the left ventricle, the part of the heart that pumps oxygenated blood around the body, and is the most important for survival. Alternatively, an artery such as the radial artery from the arm or gastroepiploic artery from the stomach, may be used in place of a vein. Graft patency Grafts can become diseased and may occlude in the months to years after bypass surgery is performed. Patency is a term used to describe the chance that a graft remain open. A graft is considered patent if there is flow through the graft without any significant (>70% diameter) stenosis in the graft. Graft patency is dependent on a number of factors, including the type of graft used (internal thoracic artery, radial artery, or great saphenous vein), the size or the coronary artery that the graft is anastomosing with, and, of course, the skill of the surgeon(s) performing the procedure. In generally, the best patency rates are achieved with the left internal thoracic artery, when its proximal end is unchanged, with the distal end being anastomosed with the coronary artery (typically the left anterior descending artery or a diagonal branch artery). Lesser patency rates can be expected with radial artery grafts and "free" internal thoracic artery grafts (where the proximal end of the thoracic artery is excised from its origin from the subclavian artery and re-anastomosed with the ascending aorta). Saphenous vein grafts have worse patency rates, but are more available, as the patients can have multiple segments of the saphenous vein used to bypass different arteries. History The technique was pioneered by Argentinian René Favaloro and others at the Cleveland Clinic in the late 1960s. Currently, about 500,000 CABGs are performed in the United States each year. See also | ||||||||
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