Stress thallium-201 scanning proved to be a highly sensitive and specific screening procedure for myocardial ischemia in 52 consecutive cases with coronary arteriograms. Stress thallium-201 scanning was considerably more accurate and more specific than the exercise electrocardiogram (ECG) as evidenced by a sensitivity of 83percnt; compared to 55percnt;, and a specificity of 94percnt; compared to 82percnt;. When submaximal stress tests were excluded, improved sensitivity of thallium scan to exercise ECG was 95percnt; to 64percnt; with no change in specificity. Factors producing negative thallium scans in the presence of coronary artery disease werecolon; delay in obtaining the first post-exercise scan, positioning and observing variability, severe three-vessel disease uniformly affecting all myocardial segments, and failure to achieve maximal stress testing due to attenuation of the heart-rate response by propranolol or somatic complaints.
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