Myocardial transport of hexakis(2-methoxyisobutylisonitrile) and thallium before and after coronary reperfusion.
Effects of no-flow ischemia (NFI) and reperfusion (RPF) on myocardial extraction and retention of technetium-99m hexakis(2-methoxyisobutylisonitrile) (sestamibi) and thallium-201 were investigated in 12 isolated, blood-perfused rabbit hearts with isotope dilution studies at constant coronary perfusion. After a control injection of tracers, NFI was induced for 30-60 minutes. After coronary reflow, repeat tracer injections were given at early RPF (5-15 minutes of RPF) and late RPF (40-60 minutes of RPF). After NFI-RPF, maximal fractional extraction and capillary permeability-surface area product increased for sestamibi (from +39% to 69%) and decreased for thallium (from -14% to -68%). Net extraction was 33% lower for sestamibi than for thallium at control, 13% lower at early RPF, and 90% higher than thallium at late RPF. Interstitial-myocyte exchange estimates were always higher for sestamibi than for thallium and increased for both with NFI-RPF (sestamibi, from 57.4 to 122.4 ml/min/g; thallium, from 3.1 to 22.3 ml/min/g). Intramyocyte volumes of distribution were higher for sestamibi than for thallium (greater than 200% at control, 800-1,000% with RPF), and NFI-RPF had opposite effects on the two tracers (late RPF vs. control: +28% for sestamibi, -50% for thallium). Our results suggest that sestamibi and thallium have different transport or sequestering mechanisms and that NFI-RPF had opposite effects on myocardial capillary-tissue exchange and tissue retention of sestamibi and thallium. Therefore, myocardial perfusion might be overestimated with sestamibi and underestimated with thallium during early RPF.
Meerdink
D J
DJ
Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655.
Leppo
J A
JA
D000818:Animals; D001692:Biological Transport; D002199:Capillary Permeability; D003326:Coronary Circulation; D003327:Coronary Disease / Q000378:metabolism* / Q000503:physiopathology; D006439:Hemodynamics; D066298:In Vitro Techniques; D008297:Male; D008955:Models, Cardiovascular; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D011817:Rabbits; D017256:Technetium Tc 99m Sestamibi; D013793:Thallium / Q000493:pharmacokinetics*; D013997:Time Factors
D015609:Organotechnetium Compounds; D017256:Technetium Tc 99m Sestamibi; D013793:Thallium