Thallium-20 1 myocardial perfusion scintigraphy for the clinical clarification of normal, abnormal and equivocal electrocardiographic stress tests.

Sixty-five patients were studied with stress electrocardiography and thallium-20 1 relative myocardial perfusion scintigraphy. Results were correlated with selective coronary angiography. Scintigraphy was more sensitive (85 versus 67 percent), more specific (89 versus 63 percent) and significantly more accurate (87 versus 65 percent) than stress electrocardiography for the diagnosis of significant coronary arterial lesions in patients with isoelectric S-T segments at rest. Stress scintigraphy helped clarify the equivocal stress test due to left bundle branch block, left ventricular hypertrophy, drugs, hyperventilation and other conditions and was more accurate than the stress electrocardiogram (89 versus 53 percent) even in the presence of a depressed S-t segment at rest. Thallium-20 1 scintigraphy is a safe and simple noninvasive method for identifying abnormal myocardial perfusion, stress-induced ischemia and, indirectly, significant coronary arterial lesions.