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Simple Test to Screen for Heart Attack now Available in S.C.

CHARLESTON, SC -- The Medical University of South Carolina (MUSC) will begin offering a simple screening test to predict an individual's risk of heart attack or other coronary events. The test, known as cardiac scoring, uses an ultrafast CT scan to quantify calcium deposits in the coronary artery.

Coronary artery calcium is one component of plaque and is a marker for atherosclerosis (hardening of the arteries), explained Michael E. Assey, M.D., director of the Cardiology Division. "Calcification found in the coronary artery is an indicator of atherosclerotic plaque in the lumen of the blood vessel and/or the blood vessel wall, " he said. "In general, people who don't have coronary calcification are not likely to have blockages verified by heart catheterization, and those with a lot of calcification are likely to have at least a single blockage in a major heart artery." Autopsy reports and other data have consistently shown correlation between coronary artery calcium content and the severity of coronary artery disease.

The cardiac scoring test can detect calcium deposits long before they are large enough to form an obstruction in the blood vessel lumen. The study of nearly 4,000 patients just published in Circulation, an official publication of the American Heart Association, compared results of the SPECT thallium stress test, a frequently used test which requires the injection of a radioactive substance, with the Cardiac Scoring Test. When calcium was shown to be severe according to the Cardiac Score, the SPECT test showed an abnormality only one-half of the time. "The calcium test is more sensitive," explained Assey. "It will find plaque in the blood vessel wall, whereas the thallium stress test detects blockages that have developed from the plaque and are bulky enough to limit flow through the artery. Instead of looking at the "hole in the donut," the calcium score evaluates the donut itself. This makes the test an extremely valuable screening device to identify the person who has no symptoms, but has significant plaque in the blood vessel wall. In such a case, it is not unusual for a small amount of plaque to change shape, attract a clot and result in a heart attack.

It is important that the test be done along with physician interaction to determine how to properly use the data, said Assey. There are situations where a person with a negative result could still be at risk for a heart attack. For example, an individual who smokes might not be protected from heart attack even with a low calcium score. In general, the physician looks at the results of the scan in conjunction with a variety of other information to determine the appropriate course of action. The results might lead to heart catheterization. For many patients, however, a low calcium score might lead only to a change in diet, exercise or other medication.

"The value of this screening test lies in its simplicity, " said J. Bayne Selby Jr., M.D. , an MUSC vascular radiologist. "It is one of the easiest tests in the field of medical imaging that I have seen in the last 20 years." The patient, in street clothes, lies on a table that slides him through a scanning device that looks like a large donut. The scanner records information into a computer, and the entire process is completed in about two minutes.

The computer produces a series of cross section images of the heart, including the coronary arteries. The vascular radiologist examines each of the images, carefully circling any area where calcification is observed. The computer calculates the quantity of the calcium present. The radiologist then uses this number to give the test result a "score". This score puts the patient into one of four or five categories of risk, ranging from normal to extremely high risk. "While data from other centers around the country have shown a high correlation between the cardiac score and heart disease, we wanted to validate these findings ourselves before offering the test at MUSC, " said Assey. Drs. Selby, Assey and Lee Butterfield looked at a series of MUSC patients undergoing heart catheterization for an assortment of reasons. The vascular radiologists did the cardiac scoring without knowledge of the results of the cardiac catheterization. When the results were compared, an excellent correlation was found between the two tests.

This simple screening method is relatively new and is possible because of the availability of high speed CT scanning equipment. Since the coronary arteries supply blood to the heart muscle and are in constant motion as the heart beats, the production of x-ray images of the moving vessels was not possible until the advent of the high speed equipment. The first Ultrafast CT used an electron gun with a sweeping motion to collect images. The conventional scanners need time to rotate mechanically around the patient. This can result in blurred images because of heart motion. The Ultrafast CT catches the heart between beats while the patient holds his breath.

Cardiac scoring had its beginnings in the Western United States about 10 years ago when several centers began using electron beam CT equipment to produce cardiac scoring based on calcification. But using the electronic beam CT was an extremely expensive procedure. It is only recently that the conventional CT equipment has become much faster, producing image quality capable of performing cardiac scoring. MUSC has one of these new Ultrafast Helical CT scanners and is the first center in South Carolina to offer this relatively inexpensive test. To schedule a cardiac scoring test, call 800-424-MUSC or 843-792-1414.