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

Abstract

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)

99mTc-sestamibi kinetics predict myocardial viability in a perfused rat heart model

“…However, a number of other investigators have questioned the utility of 99m Tc-sestamibi for assessment of myocardial viability [13][14][15][16][17][18][19][20][21][22]. Once again, models have ranged from cultured cells to perfused hearts, large animal models, and patient studies.…”

“…They showed that the initial uptake reflects predominantly coronary blood flow, independent of myocardial viability. A number of reports using pig and dog models of coronary occlusion followed by reperfusion also found a poor correlation of 99m Tc-sestamibi uptake with viability [13,14,18,19,21]. Despite a 24-h model of coronary occlusion, Merhi et al concluded that 99m Tc-sestamibi distribution was not significantly influenced by cell death [16].…”

“…Despite a 24-h model of coronary occlusion, Merhi et al concluded that 99m Tc-sestamibi distribution was not significantly influenced by cell death [16]. Redistribution has also been found in necrotic tissue [14]. However, it is unclear if the tracer was actively taken up, or simply trapped.…”

“…99m Tcsestamibi is widely utilized for myocardial perfusion imaging in conjunction with exercise or pharmacologic stress and has also been proposed as a viability imaging agent. Several investigators have reported the utility of 99m Tc-sestamibi for assessing myocardial viability [1][2][3][4][5][6][7][8][9][10][11][12], while a number of other investigators have questioned the utility of 99m Tc-sestamibi for assessment of myocardial viability [13][14][15][16][17][18][19][20][21][22]. Furthermore, in several of these studies, the relative contributions of flow and viability to 99m Tc-sestamibi uptake could not be determined.…”