DIPYRIDAMOLE TL-201 SCINTIGRAPHY AS A PREOPERATIVE SCREENING-TEST - A REEXAMINATION OF ITS PREDICTIVE POTENTIAL

Background. We examined the value of dipyridamole thallium-201 (Tl-201) scintigraphy as a preoperative screening test for perioperative myocardial ischemia and infarction. Methods and Results. We prospectively studied 60 patients undergoing elective vascular surgery. We performed Tl-201 scintigraphy preoperatively and blinded all treating physicians to the results. Historical, clinical, laboratory, and physiological data were gathered throughout hospitalization. Myocardial ischemia was assessed during the intraoperative period using continuous 12-lead electrocardiography (ECG) and transesophageal echocardiography (TEE) and during the postoperative period using continuous two-lead ambulatory ECG. Adverse cardiac outcomes (cardiac death, myocardial infarction, unstable angina, severe ischemia, or congestive heart failure) were assessed daily throughout hospitalization. Twenty-two patients (37%) had defects that improved or reversed on delayed scintigrams (redistribution defects), 18 (30%) had persistent defects, and 20 (33%) had no defects on Tl-201 scintigraphy. There was no association between redistribution defects and adverse cardiac outcomes: 54% (seven of 13) of adverse outcomes occurred in patients without redistribution defects, and the risk of an adverse outcome was not significantly increased in patients with redistribution defects (relative risk 1.5, 95% confidence interval 0.6-3.9, p = 0.43). Consistent with these findings, there was also no association between redistribution defects and perioperative ischemia: 54% (19 of all 35) of perioperative ECG and TEE ischemic episodes and 58% (14 of 24) of severe ischemic episodes occurred in patients without redistribution defects. The sensitivity of Tl-201 scintigraphy for perioperative ischemia and adverse outcomes ranged from 40% to 54%, specificity from 65% to 71%, positive predictive value from 27% to 47%, and negative predictive value from 61% to 82%. Conclusions. These results differ from those of previous studies and suggest that the routine use of Tl-201 scintigraphy for preoperative screening of patients undergoing vascular surgery may not be warranted.