On the Relativity of Dipyridamole and Dobutamine Flows
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Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA
Received Apr 13, 2020; accepted Apr 13, 2020 doi:10.1007/s12350-020-02309-8
See related article, https://doi.org/10.10 07/s12350-020-02186-1. Myocardial perfusion imaging with pharmacologic vasodilator stress has become an integral component of assessing the risk for future major adverse cardiac events (MACE). The addition of quantitative flows in ml/min/g to standard perfusion imaging has further refined the accuracy of predicting major adverse cardiovascular events.1 The level of flow increase during pharmacologic stress largely defines the degree of risk: a normal flow response indicates low risk whereas moderate to severe attenuations of the flow response signify increasing levels of cardiac risk.1 Pharmacologic stress typically employs vasodilators like adenosine, dipyridamole, and, most commonly, the adenosine receptor agonist regadenoson, agents that raise coronary blood flow via maximum vascular smooth muscle relaxation. When use of adenosine-related vasodilators is contraindicated, the sympathomimetic amine dobutamine serves as alternative stressor. Unlike adenosine-related agents that raise coronary flow independent of cardiac work, dobutamine increases cardiac work and thus myocardial oxygen consumption (MVO2) which prompts a commensurate metabolism-mediated rise in coronary flow in order to meet the myocardium’s increased O2 and substrate needs. Flow responses to dobutamine stimulation have been measured in the past with radiotracers of
Reprint requests: Heinrich R. Schelbert, MD, PhD, FACC, MASNC, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Box 95648B2-085J, 650 Charles E Young Drive South, Los Angeles, CA 90095-6948; hschelbert@ mednet.ucla.edu J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2020 American Society of Nuclear Cardiology.
myocardial blood flow like O-15 water or N-13 ammonia and PET.2-4 No such measurements with PET and Rubidium-82 (Rb-82) have been reported as yet, even though it is the very radiotracer that it is now most widely employed with cardiac PET in the clinical setting. Because its physical and imaging properties differ from those of O-15 water and N-13 ammonia, quantitative estimates of flow responses to dobutamine stimulation with Rb-82 would be informative and clinically useful. In the current issue of the journal, Pelletier-Galarneau et al.5 are first to report such Rb-82 PET measurements in a group of 156 patients, all of whom had been referred for evaluation of suspected or known coronary artery disease to the University of Ottawa Heart Institute from 2006 to 2016. All had undergone Rb-82 PET rest and dobutamine perfusion imaging combined with quantitative flow measurements. Median global flows at rest were 0.84 ml/min/g and were similar in four subgroups of patients, that is, (a) patients with less than 3 and (b) patients with more than 3 risk factors but without coronary artery disease; (c) patients with prior revascu
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