Quantitative myocardial perfusion and coronary reserve in rats with 13N-ammonia and small animal PET:: Impact of anesthesia and pharmacologic stress agents

The purpose of this study was to evaluate the effects of 2 anesthetic agents on myocardial perfusion and coronary reserve in rats under resting and stress conditions with small animal PET. Methods: Twenty-four rest/stress studies were performed in 6 rats. Each animal received all 4 possible combinations of anesthetic agents (propofol, isoflurane) and pharmacologic stress agents (dobutamine, adenosine) to increase myocardial perfusion. For each stress or rest study, a 10-min dynamic acquisition was performed in list mode with 185 MBq of N-13-NH3. Data analysis was performed according to a 3-compartment myocardial blood flow model. Pharmacologic stimulation by either dobutamine or adenosine was performed to increase myocardial perfusion. Results: The perfusion values (mean +/- SD) for the various experimental conditions were as follows: propofol/dobutamine, 7.8 +/- 2.4 mL/g/min (rest, 3.7 +/- 0.8 mL/g/min; mean +/- SD); isoflurane/dobutamine, 9.3 +/- 3.1 mL/g/min (rest, 4.3 +/- 1.0 mL/g/min); propofol/adenosine, 6.8 +/- 1.7 mL/g/min (rest, 3.2 +/- 0.4 mL/g/min); and isoflurane/adenosine, 5.2 +/- 1.3 mL/g/min (rest, 3.7 +/- 0.7 mL/g/min). All perfusion data showed a significant increase after pharmacologic stimulation relative to baseline (P < 0.05). The coronary reserve (mean +/- SD) measured by PET was slightly lower with the combination of isoflurane and adenosine (1.4 +/- 0.5) than with propofol and adenosine (2.1 +/- 0.5). Conclusion: Noninvasive quantitative measurements of myocardial perfusion in small animals at rest and during stress are feasible using PET. Evaluation of the coronary reserve must take into account the initial state of the anesthetized animal. The coronary reserve could be measured with both anesthetic agents using either dobutamine or adenosine stimulation.