Coronary Bypass Surgery: Definition
Coronary artery bypass surgery, also coronary artery bypass grafts and heart bypass (colloquial), is a surgical procedure performed on patients with coronary artery disease 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).
Coronary Bypass Surgery: 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).
Coronary Bypass Surgery: Prognosis
Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10-15 years.
Coronary Bypass Surgery: Complications
- Infection - at site where graft was harvested, chest
- Non-union/malunion of sternum (breast bone) WIth minimally invasive techniques this risk does not exist.
- Anesthetic complications - drug reactions (e.g. malignant hyperthermia)
- Myocardial infarction due to hypoperfusion or early graft occlusion
- Graft failure leading to myocardial infarction
- Death due to myocardial infarction, stroke, renal failure, sepsis
- Acute renal failure due to hypoperfusion
- Stroke - during reperfusion
- Stenosis of the graft (late) - particularly of saphenous vein grafts
- Keloid scarring
- Chronic pain - at incision sites
- Post-Operative Stress Related Illnesses - Constipation, Chronic Bracing, Memory Loss, Trenchmouth (see Gingivitis), Teeth Grinding etc.
In non-minimally invasive procedures, the sternum is cut down the middle with a bone saw and the chest opened (a procedure known as median sternotomy). Depending on a number of factors, the surgeon may decide to place the patient on cardiopulmonary bypass ("on-pump") or use stabilizing devices to hold the heart still while sewing the anastamoses ("off-pump"). Blood vessels are harvested from elsewhere in the body for grafting. Sometimes artery end branches supplying tissues near the heart are rerouted to create the bypass.
Coronary Bypass Surgery: Conduits
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 is 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.
Coronary Bypass Surgery: History
The coronary bypass 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.