Extent of myocardial damage in regions with reverse redistribution at 3 h and at 24 h on 201Tl SPET: evaluation based on regional myocardial oxidative metabolism.

Abstract

Reverse redistribution (RRD) of 201Tl is often observed in patients with recent myocardial infarction. However, the difference in the extent of myocardial damage between regions with 3-h RRD and those with 24-h RRD remains unknown. Accordingly, we investigated RRD from the standpoint of myocardial oxidative metabolism. Carbon-11 (11C) acetate dynamic myocardial PET scanning was performed at rest in 14 patients with recent myocardial infarction, and the clearance rate constant (Kmono) of 11C-acetate was calculated in 6-7 ROIs on the transaxial image in each patient using a monoexponential fit as an index of myocardial oxidative metabolism. Exercise 201Tl myocardial SPET was also performed. Ninety-two regions corresponding to the PET study were then classified based on the findings of transaxial 201Tl SPET imaging; that is, regions with reverse redistribution, regions with severely decreased 201Tl activity or no 201Tl activity on the 24-h delayed images, and regions with normal 201Tl activity throughout the study. Kmono in regions with reverse redistribution (0.051 +/- 0.009 min-1) was significantly lower than that in regions with normal 201Tl activity throughout the study (0.066 +/- 0.011 min-1) (P < 0.001) but significantly higher than that in regions with severely decreased or no 201Tl activity on the 24-h delayed images (0.037 +/- 0.003 min-1) (P < 0.001). Percent Kmono (i.e. Kmono in region with RRD/the mean of Kmono in all regions with a normal 201Tl SPET result) was significantly lower in the 3-h RRD regions (81.3 +/- 6.3%) than in the 24-h RRD regions (87.6 +/- 6.1%) (P < 0.05). Impairment of myocardial oxidative metabolism is observed in regions with RRD, suggesting that RRD corresponds to mild myocardial damage. Reverse redistribution on 24-h delayed images may indicate much milder myocardial damage compared with RRD on 3-h delayed images.