Heart bypass

Coronary artery bypass surgery, also known as coronary artery bypass graft (CABG, pronounced 'cabbage') surgery, and colloquially heart bypass or bypass surgery, is a surgical procedure to restore normal blood flow to an obstructed coronary artery. A normal coronary artery transports blood to and from the heart muscle itself, not through the main circulatory system.Illustration depicting coronary artery bypass surgery (double bypass)Illustration of Single bypassIllustration of Double bypassIllustration of Triple bypassIllustration of Quadruple bypass Coronary artery bypass surgery, also known as coronary artery bypass graft (CABG, pronounced 'cabbage') surgery, and colloquially heart bypass or bypass surgery, is a surgical procedure to restore normal blood flow to an obstructed coronary artery. A normal coronary artery transports blood to and from the heart muscle itself, not through the main circulatory system. There are two main approaches. In one, the left internal thoracic artery, LITA (also called left internal mammary artery, LIMA) is diverted to the left anterior descending branch of the left coronary artery. In this method, the artery is 'pedicled' which means it is not detached from the origin. In the other, a great saphenous vein is removed from a leg; one end is attached to the aorta or one of its major branches, and the other end is attached to the obstructed artery immediately after the obstruction to restore blood flow. CABG is performed to relieve angina unsatisfactorily controlled by maximum tolerated anti-ischemic medication, prevent or relieve left ventricular dysfunction, and/or reduce the risk of death. CABG does not prevent myocardial infarction (heart attack). This surgery is usually performed with the heart stopped, necessitating the usage of cardiopulmonary bypass. However, two alternative techniques are also available, allowing CABG to be performed on a beating heart either without using the cardiopulmonary bypass, a procedure referred to as 'off-pump' surgery, or performing beating surgery using partial assistance of the cardiopulmonary bypass, a procedure referred to as 'on-pump beating' surgery. The latter procedure offers the advantages of the on-pump stopped and off-pump while minimizing their respective side-effects. CABG is often indicated when coronary arteries have a 50 to 99 percent obstruction. The obstruction being bypassed is typically due to arteriosclerosis, atherosclerosis, or both. Arteriosclerosis is characterized by thickening, loss of elasticity, and calcification of the arterial wall, most often resulting in a generalized narrowing in the affected coronary artery. Atherosclerosis is characterized by yellowish plaques of cholesterol, lipids, and cellular debris deposited into the inner layer of the wall of a large or medium-sized coronary artery, most often resulting in a partial obstruction in the affected artery. Either condition can limit blood flow if it causes a cross-sectional narrowing of at least 50 percent. There are many variations in terminology, in which one or more of 'artery', 'bypass' or 'graft' is left out. The most frequently used acronym for this type of surgery is CABG (pronounced 'cabbage'), pluralized as CABGs (pronounced 'cabbages'). Initially the term aortocoronary bypass (ACB) was more popularly used to describe this procedure. CAGS (coronary artery graft surgery, pronounced phonetically) should not be confused with coronary angiography (CAG). The terms single bypass, double bypass, triple bypass, quadruple bypass and quintuple bypass refer to the number of coronary arteries bypassed in the procedure. In other words, a double bypass means two coronary arteries are bypassed (e.g., the left anterior descending (LAD) coronary artery and right coronary artery (RCA)); a triple bypass means three vessels are bypassed (e.g., LAD, RCA and left circumflex artery (LCX)); a quadruple bypass means four vessels are bypassed (e.g., LAD, RCA, LCX and first diagonal artery of the LAD) while quintuple means five. Left main coronary artery obstruction requires two bypasses, one to the LAD and one to the LCX. A coronary artery may be unsuitable for bypass grafting if it is small (< 1 mm or < 1.5 mm), heavily calcified, or located within the heart muscle rather than on the surface. A single obstruction of the left main coronary artery is associated with a higher risk for a cardiac death and usually receives a double bypass. The surgeon reviews the coronary angiogram prior to surgery and identifies the number of obstructions, the percent obstruction of each, and the suitability of the arteries beyond the obstruction(s) as targets. The presumed number of bypass grafts needed as well as the location for graft attachment is determined in a preliminary fashion prior to surgery, but the final decision as to number and location is made during surgery by direct examination of the heart. Age per se is not a factor in determining risk vs benefit of CABG.