Comparison of stress myocardial Flow Response using regadenoson and dipyridamole in SPECT

Introduction: Regadenoson is a selective A2A adenosine receptor agonist, widely used, but more expensive than dipyridamole. We compared dipyridamole and regadenoson Myocardial Blood Flow (MBF) and Myocardial Flow Reserve (MFR) values obtained with dynamic Cadmium Zinc Telluride (CZT) SPECT Myocardial Perfusion Imaging (MPI), to evaluate if they could induce the same level of hyperemia on a population with low cardiovascular risk. Materials and Methods: Patients referred for dynamic MPI between November 2018 and March 2020 were retrospectively analyzed. SPECT data were acquired on a CZT camera (Discovery NM 530c, GE Healthcare, Haïfa, Israël), using 1-day stress/rest 99mTc-tetrofosmin dynamic protocol. All analysis was performed using Corridor 4DM. Patients suffering from CAD or with high cardiovascular risk tend to have reduced stress MBF and MFR. To rule out confounding factors and emphasize differences between stress agents, patients with prior cardiac disease, ischemia or infarction and diabetes were excluded. The remaining patients were matched for clinical characteristics (age, gender, BMI, cardiovascular risk factors) and compared in terms of stress MBF and MFR.

Results: Two groups of 40 patients with low-cardiovascular risk, comparable in terms of age, gender, BMI, resting left ventricular ejection fraction, cardiac risk factors and cardiovascular treatments at the time of evaluation were analyzed. Mean global MFR wasn’t different between the two groups: 2.62 ± 0.8 and 2.46 ± 0.8 respectively for dipyridamole and regadenoson (p=0.88). Stress MBF wasn’t significantly different either between dipyridamole (1.57 ± 0.6 ml/min/g) and regadenoson patients (1.61 ± 0.6 ml/min/g) (p=0.88).

Conclusions: Dipyridamole and regadenoson induced equivalent hyperemia with similar global stress MBF and MFR on a low-risk population without confounding factors. These results should be confirmed on a large, prospective and randomized study, including healthy young patients and also high risk patients.