Time course of technetium-99m sestamibi myocardial distribution in dogs with a permanent or transient coronary occlusion.

The influence of duration of coronary occlusion and reperfusion on technetium-99m hexakis-2-methoxyisobutylisonitrile (99mTc-sestamibi) myocardial redistribution between necrotic, salvaged and non-ischaemic myocardium was investigated in dogs submitted either to a 90-min or a 24-h permanent left descending coronary artery occlusion (groups 1 and 2) or to a 90-min occlusion followed by 30 min, 6 h or 22.5 h of reperfusion (groups 3, 4 and 5). In all groups, 99mTc-sestamibi and radiolabelled microspheres were injected at 45 min of occlusion. After delimiting the area at risk and the infarct by Evans blue perfusion and triphenyltetrazolium chloride staining, radioactivity of heart slices from normal, viable-ischaemic and necrotic myocardium was measured in a gamma counter. A significant (P < 0.001) linear relationship between 99mTc-sestamibi distribution and myocardial blood flow was observed in the area at risk of groups 1 (r = 0.92), 2 (r = 0.84), 3 (r = 0.90), 4 (r = 0.93) and 5 (r = 0.58). In all groups, the mean percentage of 99mTc-sestamibi uptake in the ischaemic over normal zone overestimated significantly (P < 0.05) the mean percentage of the ratio in myocardial blood flow measured with microspheres (group 1: 13.3 +/- 1.4 vs. 7.7 +/- 1.2; group 2: 15.9 +/- 2.0 vs 5.6 +/- 1.2; group 3: 14.9 +/- 1.6 vs 6.2 +/- 1.0; group 4: 20.9 +/- 1.7 vs 10.9 +/- 1.8; group 5: 51.0 +/- 2.7 vs 14.0 +/- 2.0).(ABSTRACT TRUNCATED AT 250 WORDS)