Vasodilators and myocardial blood flow by CZT cameras: Make us see further
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Department of Advanced Biomedical Sciences, University Federico II, Naples, Italy Institute of Biostructure and Bioimaging, National Council of Research, Naples, Italy
Received Sep 1, 2020; accepted Sep 1, 2020 doi:10.1007/s12350-020-02369-w
See related article, https://doi.org/10.10 07/s12350-020-02271-5. In nuclear cardiology the pharmacological stressors have been extensively used in all those conditions in which physical stress test is not indicated. The most used medications for stress myocardial perfusion imaging (MPI) are vasodilators, which carry out their role of activating adenosine receptors and consequently increasing myocardial blood flow.1 Adenosine activates all four receptor subtypes (A1, A2A, A2B and A3).1 A2A receptors are the subtype that mediates the coronary vasodilator effect, whereas the other subtypes are located in different organs and are responsible for the majority of the adverse side effects such as mast cell degranulation, bronchoconstriction (A2B and A3), and negative chronotropic and inotropic effect (A1). Dipyridamole has the longest history of use among all the vasodilators with consistent data available in the literature referencing its use in MPI.2 Dipyridamole acts on all adenosine receptor subtypes and it has a longer half-life as compared to adenosine, but it may lead to undesirable side effects: flushing, headache, dizziness, hypotension, and atrio-ventricular block. Thus, aminophylline may be required (125-250 mg) in order to reduce adverse symptoms of prolonged duration. Recently, regadenoson has been introduced in clinical practice as a selective stimulator of A2A receptors, which determine coronary vasodilation limiting the side effects. Regadenoson has several advantages, such as the
Reprint requests: Wanda Acampa, MD, PhD, Department of Advanced Biomedical Sciences, University Federico II, Via Pansini 5, 80131 Naples, Italy; [email protected] J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2020 American Society of Nuclear Cardiology.
easy administration modality (bolus in standardized dose of 0.4 mg, regardless of body weight)3 and its good tolerability profile in all patients, especially in those affected by chronic obstructive pulmonary disease, which may contraindicate other vasodilators.4 It has been demonstrated that regadenoson MPI provides comparable results for detecting reversible defects as compared to a standard adenosine infusion, without serious drug-related side effects.5 After a single bolus infusion, hyperemia is maintained significantly longer than with adenosine facilitating radionuclide distribution for MPI studies. Regadenoson has also been compared to dipyridamole in various studies evaluating diagnostic performance of quantitative perfusion and functional findings using both single-photon emission computed tomography (SPECT) and PET6,7 showing an equivalency in the identification of perfusion defects. In the last decades, cardiac PET using different pharmacologic agents has been used to calculate myocardial blood flow (MBF) and myocardial perfusion r
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