• Kazuya Takehana, George A Beller, Mirta Ruiz, Frank D Petruzella, Denny D Watson, and David K Glover.
• Experimental Cardiology Laboratory, Cardiovascular Division, Department of Internal Medicine, University of Virginia Health System, Charlottesville, VA 22908-0500, USA.
• J Nucl Cardiol. 2003 Jul 1; 10 (4): 375-84.

BackgroundWe sought to determine whether a dual-isotope imaging strategy (rest thallium 201/stress technetium 99m sestamibi) might be useful for assessing myocardial viability and residual ischemia in the infarct zone very early after reperfusion.Methods And ResultsFifteen open-chest dogs had left anterior descending coronary artery occlusion for 60 minutes, followed by full reperfusion (group 1, n = 8) or reperfusion through a residual critical stenosis (group 2, n = 7). Tl-201 was injected at rest 45 minutes after reperfusion, and initial and 2-hour redistribution images were acquired. Tc-99m sestamibi was then injected during vasodilator stress, followed by imaging. Infarct size was similar in both groups (risk area, 21% +/- 4% vs 22% +/- 3%). Rest Tl-201 defect count ratios (left anterior descending coronary artery/left circumflex artery) were comparable (0.71 +/- 0.03 vs 0.74 +/- 0.02) and reflected infarct size. With vasodilation, Tc-99m sestamibi defect count ratio in group 1 (0.71 +/- 0.02) was comparable to rest Tl-201 and was significantly greater than in group 2 (0.62 +/- 0.02) with residual stenoses (P <.01). Although vasodilator Tc-99m sestamibi imaging unmasked the presence of residual stenoses, Tc-99m sestamibi uptake underestimated their functional severity (flow ratio, 0.38 +/- 0.03).ConclusionsDual-isotope imaging very early after reperfusion may have limited utility for detecting residual stenoses in the infarct zone. Underestimation of the flow disparity by Tc-99m sestamibi may make the detection of stenoses more difficult, and impaired flow reserve after ischemic insult may complicate the detection of fully reperfused segments.

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