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NOVEL SCREENING TEST PROVES EFFECTIVE FOR DETECTING HEART DISEASE IN OUTPATIENTS

A faster, less expensive screening tool for heart disease has proven effective in outpatients, according to a study presented today by researchers from University of Virginia Health System at the American Heart Association's 72nd Scientific Sessions in Atlanta. The non-invasive technique, myocardial contrast echocardiography (MCE), could provide physicians with an improved mass screening test for early detection of coronary heart disease, the number one killer of American men and women.

Because the traditional test for checking blood flow to the heart is expensive and time consuming, typically only those with symptoms are tested. The safety and convenience of MCE will allow physicians to screen those with early stage heart disease on an outpatient basis, said Dr. Sanjiv Kaul, director of the U.Va. Cardiac Imaging Center.

MCE uses microbubbles as contrast agents that scatter ultrasound during their transit through the coronary microcirculation. The microbubbles are made of insoluble, high-molecular weight gases and are about the size of a red blood cell. They are injected into a vein and flow with the blood into the heart through the coronary arteries. The signal or backscatter produced by the bubbles can be detected and measured, telling physicians the velocity of blood flowing through the heart.

The speed of blood flow through the heart is indicative of the amount of artery blockage. If there is no flow, we know there is blockage in the coronary arteries. Most people who die from heart attack have clogged arteries, Kaul explained.

In the study, which was conducted at U.Va. Health System in Charlottesville, 100 outpatients were tested using MCE and single photon emission computed tomography (SPECT). SPECT, the traditional method for measuring blood flow, uses radioisotopes that are injected into the circulatory system and picked up through a metabolic process by cells in the heart. Once the radioisotopes are in the cells, a gamma camera is used to take pictures of the heart.

Patients were tested with MCE and SPECT at rest and following an infusion of dipyridamole, a drug used to increase blood flow to the heart. The study showed similar results for MCE and SPECT.

Being able to test patients for heart disease on an outpatient is very exciting. About 5 million people come to the emergency room annually with chest pain. MCE will help emergency room physicians better diagnose those suffering a heart attack. That will lead to reduced costs and better patient care, explained Dr. John M. Dent, director of the U.Va. Stress Testing Laboratory and Echocardiography.

SPECT costs between $1,000 and $2,000 and takes half to a full day to complete; whereas, MCE costs only $300 to $400 and takes around half an hour. SPECT is not generally available in physicians' offices because a special license is required to inject radioisotopes, while ultrasound, used in MCE, is readily available to cardiologist and even primary care physicians. In addition, unlike SPECT, MCE involves no radiation, reducing patient risk.

In the study, MCE was performed using OPTISONTM, a novel ultrasound contrast agent distributed by Mallinckrodt Inc. of St. Louis and manufactured by Molecular Biosystems Inc. of San Diego.

Researchers at U.Va. plan to conduct additional studies to further refine the technique. It is expected to be available to physicians in the next one to two years.

November 9, 1999