Myocardial uptake of (99m)Tc-N-NOET and (201)Tl during dobutamine infusion. Comparison with adenosine stress.
BACKGROUND
The myocardial uptake of (99m)Tc-sestamibi is attenuated by dobutamine stress, resulting in underestimation of ischemia. N-Ethyl-N-ethoxy-dithiocarbamato-N-(99m)Tc ((99m)Tc-N-NOET) is a new (99m)Tc-labeled perfusion agent that is highly extracted by the myocardium by a mechanism different from that defined for (99m)Tc-sestamibi. We therefore hypothesized that (99m)Tc-N-NOET uptake would not be attenuated by dobutamine and that (99m)Tc-N-NOET uptake would be comparable to (201)Tl uptake during dobutamine stress.


RESULTS
In 28 open-chest dogs, after placement of a stenosis in the left anterior descending coronary artery that reduced flow reserve by >50%, adenosine (300 microgram. kg(-1). min(-1); n=15) or dobutamine (2.5 to 30 microgram. kg(-1). min(-1); n=13) was infused. During adenosine stress, the stenotic-to-normal activity ratio for (99m)Tc-N-NOET was 0.55+/-0.05. The stenotic-to-normal flow ratio was 0.33+/-0.04 at the time of (99m)Tc-N-NOET injection. During dobutamine stress, the stenotic-to-normal (99m)Tc-N-NOET activity ratio was 0.63+/-0.04, comparable to the (201)Tl activity ratio of 0.59+/-0.04. The stenotic-to-normal flow ratio was 0.47+/-0.04 at the time of (99m)Tc-N-NOET and (201)Tl injection. The relationship between (99m)Tc-N-NOET uptake and blood flow was comparable for adenosine and dobutamine stress, with no evidence of attenuation of (99m)Tc-N-NOET extraction by dobutamine. Conclusions-In the presence of coronary stenoses that reduced regional flow reserve, the myocardial uptake of (99m)Tc-N-NOET and (201)Tl are closely proportional to blood flow during both adenosine and dobutamine stress, suggesting that the adverse effect of dobutamine on (99m)Tc-sestamibi uptake is a tracer-specific phenomenon rather than a generalized effect. The clinical implication of this finding is that (99m)Tc-N-NOET might be preferable to (99m)Tc-sestamibi when used with dobutamine stress for detection of coronary stenoses.
Calnon
D A
DA
Experimental Cardiology Laboratory, Department of Medicine, University of Virginia Health Sciences Center, Charlottesville, USA.
Ruiz
M
M
Vanzetto
G
G
Watson
D D
DD
Beller
G A
GA
Glover
D K
DK
D000241:Adenosine / Q000494:pharmacology* / Q000633:toxicity; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D004195:Disease Models, Animal; D004280:Dobutamine / Q000494:pharmacology* / Q000633:toxicity; D004285:Dogs; D004347:Drug Interactions; D006321:Heart / Q000000981:diagnostic imaging / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D013312:Stress, Physiological / Q000139:chemically induced / Q000378:metabolism; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics; D013794:Thallium Radioisotopes / Q000493:pharmacokinetics*; D013859:Thiocarbamates / Q000493:pharmacokinetics*
D015609:Organotechnetium Compounds; D013794:Thallium Radioisotopes; D013859:Thiocarbamates; D004280:Dobutamine; D017256:Technetium Tc 99m Sestamibi; D000241:Adenosine; C093922:technetium Tc 99m, bis(N-ethoxy-N-ethyldithiocarbamato)nitrido-