Efficacy of exercise thallium-201 scintigraphy in the diagnosis and prognosis of coronary artery disease (position paper, American College of Physicians)

Article Abstract:

The Clinical Efficacy Assessment Project of the American College of Physicians evaluates and informs College members about the safety and effectiveness of various diagnostic and treatment practices. This report analyzes the usefulness of exercise thallium-201 myocardial (heart) perfusion scintigraphy. A Clinical Review article on the same topic by Kotler and Diamond in the November 1, 1990 issue of the Annals of Internal Medicine provides references and support for many of the statements in this report. Thallium scintigraphy is usually conducted with electrocardiography (ECG). At the peak of exercise, the patient is usually given a dose of thallium-201, a radioactive compound that is structurally similar to potassium. Exercise is then continued for up to a minute, followed by imaging, which is generally repeated two to four hours later. The time before tissue uptake of thallium-201 and the extent of uptake are indicative of whether heart tissue is alive or dead and whether the region has full blood circulation. The technique may be limited by the interference of bone and other structures. Hazards associated with thallium scintigraphy include radiation, which is less than that associated with cardiac catheterization, and other risks similar to those associated with conventional ECG exercise testing. Thallium scintigraphy, like other diagnostic techniques, provides useful prognostic information about a patient's risk for heart attack or cardiac-related death. The value of this information is greatest for patients in whom the uncertainty is greatest. Each test improves total prognostic accuracy, but none is perfectly accurate. Compared with exercise ECG, thallium scintigraphy can modestly improve the accuracy of coronary artery disease (CAD) diagnosis. Exercise thallium scintigraphy is most useful in CAD diagnosis when other indicators have suggested an intermediate risk of disease, but is not appropriate for screening patients with a low risk of CAD. Thallium scintigraphy is probably of greatest value for examining heart attack patients who have no overt medical signs of poor heart circulation or function. (Consumer Summary produced by Reliance Medical Information, Inc.)

Reports, American College of Physicians

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Exercise thallium-201 scintigraphy in the diagnosis and prognosis of coronary artery disease

Article Abstract:

In scintigraphy a special camera produces two-dimensional images of the distribution of a radioactive substance that is injected into the body to determine the outline and function of organs in which the substance collects. Thallium-201 is a radioactive substance used in scintigraphy. The perfusion of heart tissue with thallium-201 is increasingly being used with exercise to diagnose coronary artery disease (CAD) and determine the prognosis of patients with known or suspected (CAD). This article reviews the literature concerning thallium-201 scintigraphy. The scintigram is usually conducted in conjunction with treadmill exercise and electrocardiography (ECG), and repeat images are generally taken three to four hours after exercise. Heart uptake of thallium is influenced by tissue viability and regional blood flow. The limitations, safety, and accuracy of the technique are described. The accuracy of CAD diagnosis with thallium-201 scintigraphy is variable, and technical variations in the technique are discussed. Certain groups of patients benefit from this noninvasive approach, including those with abnormal resting ECGs and restricted exercise tolerance. Although it is useful when the probability of CAD is intermediate, it is not helpful in evaluating low-risk patients. The prognostic value of using scintigraphy to assess heart attack victims and patients with a high risk of CAD is noteworthy, but whether it is the most cost effective strategy available is unclear. Current patterns of usage are described. The technique requires further investigation to determine its true practical value and accuracy as a tool for diagnosing and providing prognostic indications for patients with CAD. (Consumer Summary produced by Reliance Medical Information, Inc.)

Economic aspects

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Alternative perspectives on the biased foundations of medical technology assessment

Article Abstract:

Medical technology assessment may need to distinguish between the treatment of individuals and treatment of groups to be more effective. Evaluations of different types of medical technology are performed on groups of patients. The groups of patients participating in these studies are very select, and the testing conditions are usually optimal. These types of studies may be biased because they are oriented more towards the group rather than towards the individual. This orientation may influence the design, analysis and clinical applicability of these studies. More emphasis may need to be placed on the effectiveness of a medical technology rather than its efficacy. Additional changes that may need to take place include an emphasis on clinical importance rather than statistical significance and a shift towards objective rather than subjective outcome.

Usage, Clinical trials, Quality management, Medical technology

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