Coronary artery bypass graft (CABG) surgery is advised for selected groups of patients with significant narrowings and blockages of the heart arteries (coronary artery disease). CABG surgery creates new routes around narrowed and blocked arteries, allowing sufficient blood flow to deliver oxygen and nutrients to the heart muscle.
Coronary artery disease (CAD) occurs when atherosclerotic plaque (hardening of the arteries) builds up in the wall of the arteries that supply the heart. This plaque is primarily made of cholesterol but plaque accumulation can be accelerated by smoking, high blood pressure, elevated cholesterol, and diabetes.
Patients are at higher risk if they are older (greater than 45 years for men and 55 years for women), or if they have a positive family history for early heart artery disease. The atherosclerotic process causes significant narrowing in one or more coronary arteries.
When coronary arteries narrow more than 50 to 70%, the blood supply beyond the plaque becomes inadequate to meet the increased oxygen demand during exercise.
Then the heart muscle in the territory of these arteries becomes starved of oxygen (ischemic) and patients often experience chest pain (angina) when the blood oxygen supply cannot keep up with demand but 25% of patients have “silent” angina and have no chest pain at all despite documented lack of adequate blood and oxygen supply.
When a blood clot (thrombus) forms on top of this plaque, the artery becomes completely blocked causing a heart attack.
When arteries are narrowed in excess of 90 to 99%, patients often have accelerated angina or angina at rest (unstable angina) which can also occur due to intermittent blockage of an artery by a thrombus that eventually is dissolved by the body's own protective clot-dissolving system.
In the diagnosis of coronary artery disease, helpful tests include resting electrocardiogram (EKG), exercise treadmill test, echocardiography (ultrasound imaging of the heart muscle), and coronary angiography.
Three commonly used classes of drugs used to treat angina are:
- Beta blockers
- Calcium blockers
Unstable angina is also treated with aspirin and the intravenous blood thinner heparin because aspirin prevents clumping of platelets, while heparin prevents blood clotting on the surface of plaques in a critically narrowed artery.
CABG surgery is ideal for patients who have failed medical therapy and are not good candidates for angioplasty (PTCA), for patients with multiple narrowings in multiple coronary artery branches, such as is often seen in patients with diabetes.
During surgery involving a healthy artery or vein from the body, the most commonly used vessel is the saphenous vein from the leg, is connected, or grafted, to the blocked coronary artery. The grafted artery or vein bypasses (that is, goes around) the blocked portion of the coronary artery. This creates a new passage, and oxygen-rich blood is routed around the blockage to the heart muscle.
CABG surgery takes about four hours to complete. The aorta is clamped off for about 60 minutes and the body is supported by cardiopulmonary bypass for about 90 minutes. Patients usually get out of bed and are transferred out of intensive care the day after surgery.
The average length of stay in the hospital for CABG surgery has been reduced from as long as a week to only three to four days in most patients.Many young patients can even be discharged home after two days.
Sutures are removed from the chest prior to discharge and from the leg (if the saphenous vein is used) after 7 to 10 days and then patients are advised to wear elastic support stockings during the day for the first four to six weeks after surgery and to keep their leg elevated when sitting.
Healing of the breastbone takes about six weeks and is the primary limitation in recovering from CABG surgery. Patients are advised not to lift anything more than 10 pounds or perform heavy exertion during this healing period. Return to work usually occurs after the six-week recovery, but may be much sooner for non-strenuous employment.