UNLABELLED: Reperfusion is often incomplete after recanalization therapy because of the presence of residual coronary stenoses. Detecting mild to moderate stenoses requires assessing coronary flow reserve with vasodilator stress. 99mTc-(N-ethoxy-N-ethyl-dithiocarbamato)nitrido (N-NOET) is a viability-independent flow tracer and thus may be well suited for assessing coronary flow reserve in the acute phase of reperfusion. METHODS: Twelve open-chest dogs underwent 60 min of total left anterior descending artery (LAD) occlusion followed by either full reperfusion (group 1; n = 4) or reperfusion through a residual critical stenosis (group 2; n = 8). 99mTc-N-NOET was given during peak vasodilator stress 165 min after reperfusion, and initial and 60-min delayed images were acquired. Regional blood flow was assessed with radiolabeled microspheres. RESULTS: Infarct size was similar in both groups (9% +/- 2% vs. 8% +/- 2% of left ventricle). Both initial (0.61 +/- 0.02 vs. 0.73 +/- 0.01; P < 0.01) and 60-min (0.67 +/- 0.02 vs. 0.80 +/- 0.01; P < 0.01) defect count ratios (LAD/left circumflex coronary artery [LCx]) differentiated between the 2 groups, reflecting the greater diminution in coronary flow reserve in group 2 dogs (LAD/LCx flow ratios = 0.37 +/- 0.04 vs. 0.57 +/- 0.09; P < 0.01). Interestingly, coronary flow reserve in the reperfused zone of group 1 was diminished despite the absence of a stenosis. Thus, the difference in 99mTc-N-NOET uptake between the 2 groups was less than expected. CONCLUSION: In this canine myocardial infarction model with some coronary flow reserve preservation, 99mTc-N-NOET imaging can detect residual coronary stenoses. However, with more prolonged occlusion resulting in more severe endothelial or microvascular dysfunction, it may be difficult to distinguish varying degrees of vessel patency using any coronary flow reserve technique.
UNLABELLED: Reperfusion is often incomplete after recanalization therapy because of the presence of residual coronary stenoses. Detecting mild to moderate stenoses requires assessing coronary flow reserve with vasodilator stress. 99mTc-(N-ethoxy-N-ethyl-dithiocarbamato)nitrido (N-NOET) is a viability-independent flow tracer and thus may be well suited for assessing coronary flow reserve in the acute phase of reperfusion. METHODS: Twelve open-chest dogs underwent 60 min of total left anterior descending artery (LAD) occlusion followed by either full reperfusion (group 1; n = 4) or reperfusion through a residual critical stenosis (group 2; n = 8). 99mTc-N-NOET was given during peak vasodilator stress 165 min after reperfusion, and initial and 60-min delayed images were acquired. Regional blood flow was assessed with radiolabeled microspheres. RESULTS: Infarct size was similar in both groups (9% +/- 2% vs. 8% +/- 2% of left ventricle). Both initial (0.61 +/- 0.02 vs. 0.73 +/- 0.01; P < 0.01) and 60-min (0.67 +/- 0.02 vs. 0.80 +/- 0.01; P < 0.01) defect count ratios (LAD/left circumflex coronary artery [LCx]) differentiated between the 2 groups, reflecting the greater diminution in coronary flow reserve in group 2 dogs (LAD/LCx flow ratios = 0.37 +/- 0.04 vs. 0.57 +/- 0.09; P < 0.01). Interestingly, coronary flow reserve in the reperfused zone of group 1 was diminished despite the absence of a stenosis. Thus, the difference in 99mTc-N-NOET uptake between the 2 groups was less than expected. CONCLUSION: In this caninemyocardial infarction model with some coronary flow reserve preservation, 99mTc-N-NOET imaging can detect residual coronary stenoses. However, with more prolonged occlusion resulting in more severe endothelial or microvascular dysfunction, it may be difficult to distinguish varying degrees of vessel patency using any coronary flow reserve technique.
Authors: Kazuya Takehana; George A Beller; Mirta Ruiz; Frank D Petruzella; Denny D Watson; David K Glover Journal: J Nucl Cardiol Date: 2003 Jul-Aug Impact factor: 5.952