Correlations between uptake of technetium-99m Q12 and thallium-201: myocardial perfusion and viability in a model of acute coronary reperfusion.
To investigate whether Q12 uptake is affected by myocardial viability, as has been noted for 201Tl and sestamibi, we analyzed the initial and delayed distribution patterns of Q12 in a rat coronary artery occlusion-reperfusion model.


METHODS
Animals were intubated and ventilated, and their arterial pressures were monitored. A left thoracotomy was performed. After a 1-hr occlusion and a 1-hr reperfusion of a major branch of the circumflex artery, 201Tl and Q12 were injected intravenously. Radiolabeled microspheres were used to document the areas of risk and reperfusion. The animals were killed at 5 min or 1 hr after administration of the diffusible tracers. Tracer distribution was determined by segmental tissue analysis, and tissue viability was determined by histochemical staining.


RESULTS
Both the initial uptake and delayed retention of Q12 are sensitive to myocardial viability as shown by significantly lower uptake (28% +/- 8%) and retention (41% +/- 13%) of Q12 in the nonviable as compared to the viable segments (p < 0.001). In addition, the myocardial retention of Q12 was significantly less in the nonviable tissue when compared to the initial uptake (p < 0.01).


CONCLUSIONS
The clinical implication of these observations suggests that initial and delayed imaging after Q12 administration would reflect both the initial regional blood flow pattern and myocardial viability. Also, delayed imaging of Q12 may reflect viability better than the initial imaging.
Takahashi
N
N
Department of Medicine, University of Massachusetts Medical Center, Worcester 01655-0243, USA.
Reinhardt
C P
CP
Marcel
R
R
Leppo
J A
JA
D000818:Animals; D003326:Coronary Circulation / Q000502:physiology; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005663:Furans; D006321:Heart / Q000000981:diagnostic imaging*; D007202:Indicators and Reagents; D008297:Male; D008863:Microspheres; D015428:Myocardial Reperfusion Injury / Q000000981:diagnostic imaging*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D009580:Nitroblue Tetrazolium; D015609:Organotechnetium Compounds; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D013794:Thallium Radioisotopes
D005663:Furans; D007202:Indicators and Reagents; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes; C078496:technetium Tc 99m Q12; D009580:Nitroblue Tetrazolium