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CARDIO-VASCULAR DIAGNOSTIC WORKSHOP: SPECIAL EXAMINATIONS: HEART SCINTISCAN

This method is like the scintiscan of other organs, and is a relatively new and simple method of examination which yields a great deal of information. However, it is usually performed only in specialized medical centers.

This so-called "non-invasive" procedure does not cause any discomfort. The patient can feel only the injection of a small amount of radioactive tracer material into a vein of his arm. He is then placed under a highly sensitive instrument that detects the radioactivity and converts it into a film.

There are two basic methods for heart scintiscan. One method involves radioactive tracers which accumulate in healthy areas of the heart muscle with a sufficient blood supply, but not in the diseased areas with insufficient supply. The radioactive tracers do not accumulate in the diseased areas, because of insufficient blood supply. One such tracer is thallium which has biological features similar to potassium. The second method uses pyrophosphate which accumulates in the opposite manner in diseased tissue affected by heart attack, but not in the healthy "hot" areas.

Either way, the accumulation or lack of these materials can indicate on the film those areas in which the blood supply is insufficient and can reveal the actual size of a myocardial infarct.

The patient cannot feel the radiography as the plate registers the radioactive rays and converts them into a visible image. Thus the process may be repeated as many times as is necessary without causing the patient any discomfort. The method is time-consuming, however, because the patient must lie under the radiographic instrument during a second examination to determine the capacity of the heart to pump blood. In the treatment of coronary heart disease and myocardial infarction, the capacity of the heart to pump blood as well as its functioning and vigor are as important as the coronary circulation. The next step is to examine the ventricles, an examination which resembles the previous heart scintiscan. Radioactive albumin, which is injected before and after contraction, is detectable by radiographic instruments and converted into a radiographic image.

Since both scintiscans must be done from different angles of viewing, the procedure requires about one hour. The examination also requires that the patient fast prior to the procedure because digestive metabolism alters the biological distribution of thallium during scintiscan of the heart muscle. Since this procedure uses radioactive materials, the patient invariably raises questions about exposure, as he should. The radioactive exposure resulting from this procedure yields information about the heart that no other method can yield and the exposure is no greater than that of usual X-ray film processes. The scintiscan can be applied not only at rest, but also after physical activity, so that it is possible to determine the reaction of a damaged heart muscle to physical strain. It is also important to note that this examination can be performed on seriously ill patients following a recent heart attack. Another advantage is that the scintiscan allows determination of the location and size of a heart attack in the early stage; that is, when signs of the heart attack are not yet evident, in blood enzymes or in the EKG. A third advantage is that the examination can be repeated any time in order to carefully observe and monitor the course and progression of coronary heart disease.

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Cardio & Blood