Initial clinical experience with regadenoson, a novel selective A2A agonist for pharmacologic stress single-photon emission computed tomography myocardial perfusion imaging.
OBJECTIVE
Regadenoson, a selective A2A adenosine receptor agonist, was evaluated for tolerability and effectiveness as a pharmacological stress agent for detecting reversible myocardial hypoperfusion when combined with single-photon emission computed tomography (SPECT).


BACKGROUND
Adenosine and dipyridamole are nonselective adenosine agonists currently used as pharmacologic stressors. Despite proven safety, these agents often cause undesirable side effects and require a continuous infusion.


METHODS
This Phase II, multicenter, open-label trial was conducted in 36 patients who had demonstrated ischemia on a 6-min adenosine SPECT imaging study within the previous 2 to 46 days. Patients received regadenoson as a rapid intravenous bolus dose of 400 microg (n = 18) or 500 microg (n = 18). The radiopharmaceutical was then delivered within one minute. The SPECT images were acquired in a standard manner and uniformly processed at a central laboratory. Regadenoson and adenosine studies were presented in random order and interpreted blindly with a 17-segment model by three observers. Additionally, quantitative analysis was performed with 4D-MSPECT software (University of Michigan, Ann Arbor, Michigan).


RESULTS
Overall agreement for the presence of reversible hypoperfusion was 86%. The 400-mug dose was better tolerated. Overall, regadenoson was well-tolerated; side effects (e.g., chest discomfort, flushing, dyspnea) were generally mild in severity and self-limiting. High-grade atrioventricular block and bronchospasm were not observed.


CONCLUSIONS
Regadenoson is well-tolerated and seems as effective as adenosine for detecting and quantifying the extent of hypoperfusion observed with SPECT perfusion imaging. Phase III clinical trials are now underway, given the promise of regadenoson's reduced side effects and simplicity of bolus administration.
Hendel
Robert C
RC
Rush University Medical Center, Chicago, Illinois, USA. rhendel@midwestheart.org
Bateman
Timothy M
TM
Cerqueira
Manuel D
MD
Iskandrian
Ami E
AE
Leppo
Jeffrey A
JA
Blackburn
Brent
B
Mahmarian
John J
JJ
D000241:Adenosine; D058908:Adenosine A2 Receptor Agonists; D004562:Electrocardiography; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging*; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D010865:Pilot Projects; D011687:Purines / Q000819:agonists; D011720:Pyrazoles / Q000819:agonists; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D058908:Adenosine A2 Receptor Agonists; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D011687:Purines; D011720:Pyrazoles; D019275:Radiopharmaceuticals; C430916:regadenoson; C078700:technetium tc-99m tetrofosmin; D017256:Technetium Tc 99m Sestamibi; D000241:Adenosine