Coronary artery bypass is an effective form of treatment for people with severe narrowing of the coronary arteries from atherosclerosis. The outlook for bypass surgery is best in those who have not had a heart attack and whose hearts are not enlarged. For them, there is an 85% chance of full recovery from all symptoms, and a mortality rate, attributable to the operation, of less than 2%.

The two coronary arteries come off the main artery of the body, the aorta. The left coronary artery immediately divides into two, so there are three main coronary branches. If necessary, a bypass can be done on all three. This is called a triple bypass.

How is it performed

In the early years of bypass surgery, leg veins were used in almost all cases. The veins were connected by microsurgery to the coronary arteries beyond the narrowed areas and then linked to the high-pressure artery, the aorta, just above the heart.

An alternative procedure, now favoured by most vascular surgeons, is to connect an internal artery of the chest wall to the diseased coronary artery. Sometimes just a segment of the artery is used. The long-term results are usually excellent.

The latest development in bypass surgery is minimally invasive coronary bypass surgery. In this procedure the bypass operation is done by keyhole (laparoscopic) surgery without stopping the heart. Special instruments that can be passed though narrow ports are used and the surgeon observes the interior on a video monitor. The method is not suitable for all patients.

Metal or plastic devices called stents (small tubes) are increasingly being used to hold coronary arteries open.

Why is it necessary

People with sufficiently narrowed coronary arteries have severe chest pain on exertion (angina pectoris). They are much less able to exert themselves, and are at risk from a complete blockage of one or more of the coronary arteries (coronary thrombosis), which causes an immediate heart attack.

The operation is done on selected patients in whom the long-term risk of not doing the operation is considered to be substantially greater than the operative risks.