Myocardial imaging with intravenously injected thallium-201 in patients with suspected coronary artery disease: analysis of technique and correlation with electrocardiographic, coronary anatomic and ventriculographic findings

Abstract

Myocardial imaging was performed after intravenous injection of thallium-201 at rest in 50 patients with suspected coronary artery disease and the results were compared with electrocardiographic, ventriculographic and coronary arteriographic findings. The thallium-201 myocardial images were of good quality and compared favorably with images previously obtained with intracoronary particle injection. Myocardial to background ratios averaged 2:1, a considerable improvement over ratios reported with potassium-43. There was complete intra- and interobserver agreement in the interpretation of images in 90 and 82 percent of cases, respectively. Major disagreement occurred in less than 5 percent of cases. Overall, 15 (30 percent) had an abnormal, 10 patients (20 percent) a borderline abnormal and 25 patients (50 percent) a normal myocardial image. Of patients with electrocardiographic Q waves, 91 percent had an image defect. Of 39 patients without Q waves, 13 percent had an image defect. All 30 patients with a normal or borderline abnormal thallium-201 image had a normal ventricular contraction pattern. All patients with a segmental ventriculographic abnormality had an image defect. In all cases, the area of electrocardiographic or ventriculographic abnormality corresponded to the area of the thallium-201 image defect. The systolic ejection fraction was depressed (0.49 +/- 0.18 [mean +/- standard deviation]) in patients with an image defect compared with that in patients with a normal image (0.64 +/- 0.06, P less than 0.005). Coronary arterial lesions were present and usually of high grade in all patients with an abnormal image; however, the presence of high grade coronary stenosis or occlusion as such correlated with image defects only to the extent that prior myocardial infraction was associated. Thus, satisfactory myocardial images at rest appear to be obtained with intravenously administered thallium-201 and electrocardiographic, ventriculographic and coronary arteriographic data suggest that image defects denote regions of prior myocardial infarction.