Why does a doctor use cardiac computed tomography?

Theodore A. Monitz, MD
Cardiology (Cardiovascular Disease)
Cardiologists generally perform two types of procedure using the CT scanner. The first is a coronary calcium score, which is a screening test, which can give the physician some idea of how much plaque has been deposited in the patient's coronary arteries. When plaque is present for many years, the body tends to calcify it. This calcium can be easily seen with a CT scan and this procedure takes very little time. The other type of procedure that has recently been developed is a coronary CT angiogram. Besides looking at the calcium in the coronary arteries, fatty deposits can also be visualized and a fairly good estimation of the severity of these blockages can be made. The CT scan also evaluates the heart muscle, sac surrounding the heart (pericardium), and the pulmonary arteries, as well as the thoracic (chest) and abdominal aorta.
Today, there are two major forms of cardiac computed tomography. The first one is called a calcium scan, which is a simple procedure and does not require the placement of an IV line and does not require the use of a contrast dye injection. A coronary calcium scan is very fast. The patient hardly has to undress and the study only takes about five to 10 minutes. It is completely painless and it has very low risk. There is no contrast dye used and therefore, there is no risk of contrast reactions. The study gives valuable information about the presence of calcium in the heart arteries-a sign of atherosclerosis-, which is the plaque buildup in the arteries, leading to heart attacks and sudden cardiac death. The amount of calcium can be quantified and expressed as the Agatston score. In general, the higher the number, the higher the risk. Only a zero calcium score is normal and any non-zero calcium score indicates the presence of calcium, or plaque, in the arteries.
The other kind of a heart CT scan is a contrast enhanced coronary CT angiogram. This is sometimes called a non-invasive heart catheterization. In this procedure, we do use an IV line and we do use a contrast dye to light up the arteries of the patient. This allows us to diagnose blockages in the heart and to look at plaques in the heart. CT angiography utilizes x-rays and therefore, has some radiation exposure associated with it. However, with the most recent available scanners, this radiation dose is quite low and typically is not more than the radiation associated with a heart catheterization and is just slightly more than the average annual radiation in the United States.

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