title: The RegEx trial: a randomized, double-blind, placebo- and active-controlled pilot study combining regadenoson, a selective A(2A) adenosine agonist, with low-level exercise, in patients undergoing myocardial perfusion imaging.
abstract: BACKGROUND
  Although vasodilator stress myocardial perfusion imaging (MPI) is increasingly performed with exercise, adenosine A(2A) receptor agonists have not been studied with exercise.
  
  
  OBJECTIVE
  To determine the safety of administering regadenoson during exercise and, secondarily, to evaluate image quality, patient acceptance, and detection of perfusion defects.
  
  
  METHODS
  Patients requiring pharmacologic MPI received a standard adenosine-supine protocol (AdenoSup, n = 60) and were then randomized (2:1) in a double-blind manner to low-level exercise with bolus intravenous injection of regadenoson (RegEx, n = 39) or placebo (PlcEx, n = 21).
  
  
  RESULTS
  Adverse events occurred in 95%, 77%, and 33% of patients receiving AdenoSup, RegEx, and PlcEx, respectively. Peak heart rate was 13 beats per minute (bpm) and 21 bpm greater following RegEx compared to that following PlcEx and AdenoSup, respectively (P = .006 and <.001). Change from baseline in mean systolic blood pressure (SBP), change from baseline to nadir SBP, and percentage of patients with a decline in SBP by > or = 20 mm Hg showed no important differences between RegEx and PlcEx. No occurrences of 2nd degree or higher AV block were observed following RegEx or PlcEx; one patient developed 2nd degree AV block following AdenoSup. The mean heart-to-liver and heart-to-gut ratios were improved on RegEx vs AdenoSup: 0.85 (0.34) vs 0.65 (0.26), P < .001 and 1.1 (0.36) vs 0.97 (0.34), P < .001, respectively. Compared to AdenoSup, 70% of patients felt RegEx was much or somewhat better.
  
  
  CONCLUSIONS
  Combining regadenoson with low-level exercise is feasible, well tolerated, and associated with fewer side effects compared to AdenoSup.
authors.affiliation: Cardiology Division, Mission Internal Medical Group, 26800 Crown Valley Pkwy, Suite 120, Mission Viejo, CA 92691-6331, USA. gthomas@mimg.com
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Thomas
authors.forename: Randall C
authors.initials: RC
authors.lastname: Thompson
authors.forename: Michael I
authors.initials: MI
authors.lastname: Miyamoto
authors.forename: Tze K
authors.initials: TK
authors.lastname: Ip
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Rice
authors.forename: Douglas
authors.initials: D
authors.lastname: Milikien
authors.forename: Hsiao D
authors.initials: HD
authors.lastname: Lieu
authors.forename: Vandana S
authors.initials: VS
authors.lastname: Mathur
mesh_terms: D058917:Adenosine A2 Receptor Antagonists; D000368:Aged; D000369:Aged, 80 and over; D005080:Exercise Test; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D011687:Purines; D011720:Pyrazoles; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging*
chemical_list: D058917:Adenosine A2 Receptor Antagonists; D011687:Purines; D011720:Pyrazoles; D019275:Radiopharmaceuticals; C430916:regadenoson; D017256:Technetium Tc 99m Sestamibi