Reliability of stress thallium-201 scanning in the clinical evaluation of coronary artery disease.

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 83% compared to 55%, and a specificity of 94% compared to 82%. When submaximal stress tests were excluded, improved sensitivity of thallium scan to exercise ECG was 95% to 64% with no change in specificity. Factors producing negative thallium scans in the presence of coronary artery disease were: 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.