PROGNOSTIC VALUE OF TL-201 SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHIC MYOCARDIAL PERFUSION IMAGING ACCORDING TO EXTENT OF MYOCARDIAL DEFECT - STUDY IN 1,926 PATIENTS WITH FOLLOW-UP AT 33 MONTHS

Objectives. This study was designed to assess the prognostic value of thallium-201 single-photon emission computed tomographic graphic (thal lium SPECT) perfusion imaging in patients evaluated for stable angina pectoris and to examine the relation, if any, between the presence and extent of myocardial defect and future fatal or nonfatal cardiovascul ar events (revascularization, second myocardial infarction). Backgroun d. Compared with planar scintigraphy, thallium SPECT enables better ev aluation of the extent of myocardial perfusion defect. However, its pr ognostic value has not yet been studied in a large population of patie nts. Methods. Between 1987 and 1989 we studied 3,193 patients. After e xclusion of patients with unstable angina, myocardial infarction durin g the previous month or earlier revascularization, 1,926 patients were followed up for 33 +/- 10 (mean +/- SD) months after stress thallium SPECT imaging (performed after exercise in 1,121 patients or during di pyridamole infusion in 805 patients). Thallium SPECT imaging of the le ft ventricle was divided into six segments. Results. After normal thal lium SPECT imaging (715 patients), the annual total and cardiovascular mortality rates were, respectively, 0.42%/year and 0.10%/year and wer e significantly higher after abnormal thallium SPECT imaging (respecti vely, 2.1%, relative risk 5, p = 0.012; 1.5%, relative risk 15, p < 0. 0001 [Log rank test]). There was a significant relation between the nu mber of abnormal segments and cardiovascular mortality during follow-u p (p < 0.02) or the occurrence of nonfatal events (p < 0.001). The ext ent of defect on the initial scan provided the best SPECT variable for long-term prognosis. Thallium SPECT imaging provided additive prognos tic information compared with other clinical variables (gender, previo us myocardial infarction) and exercise electrocardiogram. Conclusions. In patients with stable angina, normal thallium SPECT imaging indicat es a low risk patient, and the extent of myocardial defect is an impor tant prognostic predictive factor.