Comparison With Adenosine Stress

Background—The myocardial uptake of Tc-sestamibi is attenuated by dobutamine stress, resulting in underestimation of ischemia. N-Ethyl-N-ethoxy-dithiocarbamato-N-Tc (Tc-N-NOET) is a new Tc-labeled perfusion agent that is highly extracted by the myocardium by a mechanism different from that defined for Tc-sestamibi. We therefore hypothesized that Tc-N-NOET uptake would not be attenuated by dobutamine and that Tc-N-NOET uptake would be comparable to Tl uptake during dobutamine stress. Methods and 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 mg z kg z min; n515) or dobutamine (2.5 to 30 mg z kg z min; n513) was infused. During adenosine stress, the stenotic-to-normal activity ratio for Tc-N-NOET was 0.5560.05. The stenotic-to-normal flow ratio was 0.3360.04 at the time of Tc-N-NOET injection. During dobutamine stress, the stenotic-to-normal Tc-N-NOET activity ratio was 0.6360.04, comparable to the Tl activity ratio of 0.5960.04. The stenotic-to-normal flow ratio was 0.4760.04 at the time of Tc-N-NOET and Tl injection. The relationship between Tc-N-NOET uptake and blood flow was comparable for adenosine and dobutamine stress, with no evidence of attenuation of Tc-N-NOET extraction by dobutamine. Conclusions—In the presence of coronary stenoses that reduced regional flow reserve, the myocardial uptake of Tc-N-NOET and Tl are closely proportional to blood flow during both adenosine and dobutamine stress, suggesting that the adverse effect of dobutamine on Tc-sestamibi uptake is a tracer-specific phenomenon rather than a generalized effect. The clinical implication of this finding is that Tc-N-NOET might be preferable to Tc-sestamibi when used with dobutamine stress for detection of coronary stenoses. (Circulation. 1999;100:1653-1659.)