Transient Defects in the Infarcted and Remote Myocardium, as Assessed by Thallium-201 Scintigraphy in Young Men after Myocardial Infarction

Abstract

This study was performed in order to assess the optimal quantitative criteria of transient defects to detect coronary stenosis with a diameter reduction of ≥ 50% in areas remote from myocardial infarction (MI), and in order to evaluate the presence of transient defects, indicating residual ischemia, in infarcted regions. Ninety-four men aged 30–44 years were examined by planar imaging thallium-201 scintigraphy following exercise and coronary angiography after MI. The coronary angiograms were scored with respect to the presence of distinct stenosis in 15 proximal segments. Transient thallium defects were quantitatively assessed and defined as the difference in relative uptake of thallium-201 at 4 h after and immediately after exercise. We found that the optimal criteria of remote transient defects in anterior regions corresponded to a sensitivity of 59% and a specificity of 52% for left anterior descending coronary artery (LAD) stenoses, in lateral regions to 81 and 60% for left circumflex coronary artery (LCX) stenoses and in inferior regions to 82 and 61% for right coronary artery stenoses. Subsequently the same criteria were applied to assess the number of transient defects in myocardial segments with a decreased (<0.80) relative uptake of thallium 4 h after exercise. Our results showed that transient defects were present in anterior regions with permanent defects in 32 out of 42 patients. Of these 32 patients, 21 had an occlusion of the corresponding coronary artery and 9 had a 50–99% stenosis. In inferior regions, 17 out of 35 patients with permanent defects had transient defects. Of these 17 patients, 11 had a coronary occlusion and 1 patient had a significant stenosis. Among the 11 patients with permanent defects in the lateral wall of the left ventricle, 3 had transient defects; 1 of these had an occlusion and 2 significant stenoses. In conclusion, our results showed that transient defects, as assessed by quantitative analysis of planar imaging thallium scintigraphy after exercise, showed a fairly good sensitivity in detecting significant stenoses remote from infarction in both the right and the LCX, but a relatively low sensitivity for stenoses in the LAD. In addition, transient defects were frequently observed in regions with permanent defects, suggesting a high rate of residual ischemia in infarcted zones.