Clinical significance of improved persistent defect by thallium-201 reinjection imaging in the subacute phase of myocardial infarction

The clinical significance of new fill-in observed by thallium-201 (201Tl) reinjection in myocardial segments with persistent defect in the subacute phase of myocardial infarction was investigated. Seventy-five patients with subacute phase (mean 20th day) of first myocardial infarction underwent stress-redistribution-reinjection 201Tl single photon emission computed tomography (SPECT) imaging. Percentage 201Tl uptake was calculated and classified as persistent defect without fill-in even after reinjection (PD group, n = 26, 35%), persistent defect with new fill-in after reinjection REINJ (+) group, n = 19, 25%] and reversible defect RD (+) group, n = 24, 32%]. The clinical features and angiographic findings were assessed in the same phase in each group. Diameter stenosis of the infarction-related arteries by coronary angiography was 68 +/- 34% in the PD group, 31 +/- 23% in the REINJ (+) group and 83 +/- 27% in the RD (+) group p < 0.01, REINJ (+) group vs PD group and RD (+) group]. Wall motion of the infarcted myocardial segments significantly improved and the mean left ventricular ejection fraction (EF) was higher in the REINJ (+) group than in the PD group (mean EF 51% vs 43%, p < 0.01). Post infarction angina was more frequent in the RD (+) group than in the REINJ (+) group (38% vs 5%, p < 0.05). Although new fill-in-after 201Tl reinjection has been considered to indicate severe myocardial ischemia in chronic coronary disease, these results indicate that this phenomenon in viable myocardium in patients with subacute phase of myocardial infarction is not always related to residual ischemia in the infarcted myocardial area.