It is mainly used if you have angina to assess the extent and severity of the disease. It involves a procedure called catheterization.

Understanding the arteries of the heart

The heart is mainly made of special muscle. The muscle pumps blood into arteries (blood vessels) which take the blood to every part of the body.

Like any other muscle, the heart muscle needs a good blood supply. The coronary arteries take blood to the heart muscle. The coronary arteries are the first arteries to branch off the aorta. The aorta is the large artery that takes blood from the left ventricle of the heart to the body.

What is angina and what causes it?

Angina is a pain that comes from the heart. The usual cause of angina is narrowing of one or more of your coronary arteries. This reduces the blood supply to a part or parts of your heart muscle. The blood supply may be enough when you are resting. However, your heart muscle needs more blood and oxygen when it works harder. For example, when you walk fast or climb stairs, your heart rate increases to deliver the extra blood. If the extra blood that your heart needs during exertion cannot get past the narrowed arteries, the heart 'complains' with pain.

The narrowing of the arteries is caused by atheroma. Atheroma is like fatty patches or 'plaques' that develop within the inside lining of arteries. (This is similar to water pipes that get 'furred up' with scale.) Plaques of atheroma may gradually form over a number of years in one or more places in the coronary arteries. In time, these can become bigger and cause enough narrowing of one or more of the arteries to cause symptoms. (The diagram shows three narrowed sections as an example. However, atheroma can develop in any section of the coronary arteries.)

What is coronary angiography?

Coronary angiography is a special x-ray of the coronary arteries. The coronary arteries do not show up on a plain x-ray. With coronary angiography, dye is injected down the coronary arteries. The arteries and their smaller branches then show up clearly on an x-ray "like a road map". Dye is injected into the coronary arteries by using a catheter. (A catheter is a thin, flexible, hollow tube.) How this is done is described below.

Therefore, coronary angiography can show the exact site and severity of any narrowing of the coronary arteries. This helps the doctor to decide on what treatment you may need. For example, if the narrowing is mild and does not need surgery. Or, if the narrowing is severe and you should have a coronary artery bypass graft or coronary angioplasty.

How is coronary angiography done?

You lie on a couch in a catheterization room. An x-ray machine is mounted above the couch. A catheter is inserted through a wide needle or small cut in the skin into a blood vessel in the groin or arm. Local anaesthetic is injected into the skin above the blood vessel. Therefore, it should not hurt when the catheter is passed into the blood vessel. The doctor gently pushes the catheter up the blood vessel towards the heart. Low dose x-rays are used to monitor the progress of the catheter tip which is gently manipulated into the correct position. You may be able to see the progress of the catheter on the x-ray monitor.

The tip of the catheter is pushed just inside a main coronary artery. Some dye is then injected down the catheter into the artery. Several x-ray films are rapidly taken as the dye is injected (the dye shows up clearly on x-ray films). The x-ray films are recorded as a moving picture and this is called an angiogram. The angiogram shows the vessels filling with blood and the sites of any narrowing can be seen.

The tip of the catheter is then put into the other main coronary artery and the test is repeated. So, an angiogram picture is built up of each of the coronary arteries and the