Coronary artery bypass graft surgery – most commonly referred to as "bypass surgery" and sometimes called CABG (pronounced "cabbage") – is a common heart surgery that reroutes, or bypasses, blood around clogged arteries to improve blood flow and oxygen to the heart.

Blocked arteries can slow or stop blood flow through the heart's blood vessels, leading to chest pain or a heart attack. Increasing blood flow to the heart muscle can relieve chest pain and reduce the risk of heart attack.

This surgery is often performed in people who have angina (chest pain) and coronary artery disease (where plaque has built up in the arteries). During the surgery, a bypass is created by grafting a piece of a vein above and below the blocked area of a coronary artery, enabling blood to flow around the obstruction. Veins are usually taken from the leg, but arteries from the chest or arm may also be used to create a bypass graft.

A patient may undergo one, two, three or more bypass grafts, depending on how many coronary arteries are blocked. Cardiopulmonary bypass with a pump oxygenator (heart-lung machine) is used for most coronary bypass graft operations. This means that besides the surgeon, other surgical staff members include a cardiac anesthesiologist, surgical nurses, and a perfusionist. 

During the past several years, more surgeons have started performing off-pump coronary artery bypass surgery (OPCAB). In it, the heart continues beating while the bypass graft is sewn in place. In some patients, OPCAB may reduce intraoperative bleeding and the need for blood transfusion, renal complications and postoperative neurological deficits (problems after surgery).

After surgery, patients are usually enrolled in a physician-supervised program of cardiac rehabilitation. Patients are often advised to eat foods low in cholesterol and saturated fat and to avoid trans fat while increasing daily physical activity to help regain strength.