Evaluation of thallium redistribution in infarcted area in accordance with time interval from the onset of myocardial infarction

This study evaluated the relationship between the time after onset of myocardial infarction and thallium redistribution in infarcted areas in a total of 123 patients with anterior infarction who underwent exercise thallium scintiscanning. Complete or incomplete redistribution of thallium was visually evaluated for transient perfusion defect by three physicians. Ischemic and defect scores were quantitatively determined by using circumferential profile analysis. The patients were divided into three groups: 64 patients receiving thallium scintiscanning within 3 months after onset of myocardial infarction (Group A), 25 patients receiving it at 3 months to one year after that (Group B), and 34 patients receiving it one year or later (Group C). Complete and incomplete redistributions were seen in 4% and 96%, respectively, for Group A, 38% and 62% for Group B, and 53% and 47% for Group C; and the rate of incomplete redistribution was significantly higher in Group A than the other two groups. Ischemic score was 50±32 for Group A, 46±29 for Group B, and 37±19 for Group C; and defect scores for these groups were 25±16, 24±16, and 20±18, respectively. Both ischemic and defect scores tended to be lower as the time after onset of myocardial infarction was longer. Eighteen patients, comprising 7 in Group A, 4 in Group B, and 7 in Group C, were also reinjected with thallium 201 and then reimaged at rest. These scans for Group A showed a significantly lower defect scores than the conventional thallium scans. Conventional exercise thallium scintiscanning seemed to underestimate thallium redistribution when performed early after onset of myocardial infarction. (N.K.)