Article: Coronary artery bypass surgery

Early in a coronary artery bypass surgery during vein harvesting from the legs (left of image) and the establishment of bypass (placement of the aortic cannula) (bottom of image). The perfusionist and heart-lung machine (HLM) are on the upper right. The patient's head (not seen) is at the bottom.

Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue. The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.

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'),^[1] 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.

Complications

• Infection - at site where graft was harvested, chest
• Non-union/malunion of sternum (breast bone)
• 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.

Most commonly, 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.

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 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.^[2][3]

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.

History

The technique was pioneered by Argentinian René Favaloro and others at the Cleveland Clinic in the late 1960s.^[4] Currently, about 500,000 CABGs are performed in the United States each year.

See also

• Angioplasty
• Cardiothoracic surgery
• Dressler's syndrome
• Hybrid bypass