Introduction: Myocardial perfusion imaging (MPI) is widely used in the evaluation of known and suspected coronary artery disease (CAD). Imaging of heart in stress and rest enables the comparison of myocardial uptake of radiotracer in proportion to the needs and coronary flow, which is used for detection of perfusion defects. Exercise stress and pharmacologic agents are used for the stressing purpose. Novel pharmacologic stressor regadenoson is A2A selective adenosine agonist, which selectively binds to the adenosine receptors in coronary arteries causing coronary dilatation. Materials and methods: We analyzed 50 myocardial perfusion studies performed with regadenoson as a pharmacologic agent that was injected before Tc99m-sestamibi in stress imaging. Stress and rest sets of images were evaluated for relative uptake of Tc99m-sestamibi in order to detect and characterize perfusion defects. After the injection of regadenoson, hemodynamic parameters and potential side-effects were closely monitored. Side-effects were stratified per severity as mild, moderate and severe. Studies were read by nuclear medicine physicians using quantitative perfusion SPECT software. Additional diagnostic information such as wall motion and wall thickening were provided by gating. Results: Thirty-three patients (66%) experienced one or more side-effects upon the administration of regadenoson, most commonly warmth and chest discomfort. In all patients but one (98%), the symptoms were mild, of short duration and self-limiting. Out of all side-effects registered, 44 (96%) were mild, and 2 (4%) were moderate. Two moderate side-effects developed in one patient with a prior history of asthma, and included shortness of breath and cough. Heart rate changed by 16 +- 31 bpm. Highest increase in blood pressure was 30 mm Hg for systolic, and 10 mm Hg for diastolic. One case of significant decrease in blood pressure was noted from the hypertensive basal values, 50 mm for systolic, and 30 mm Hg for diastolic. ST segment depression of up to 1 mm occurred in 4 cases (8%), and T-wave changes in 3 cases (6%). No conduction abnormalities, significant hypotension, symptomatic bradycardia or cardiac arrest ocurred. Conclusion: Our first institutional experiences proved regadenoson as A2A selective adenosine agonist as a pharmacologic stressor to be safe, tolerable and easily used. Its safety profile enabled the study to be performed in patients with respiratory disease also.
Key words: myocardial perfusion imaging, regadenoson.