Safety and tolerability of regadenoson in 514 SPECT MPI patients with and without coronary artery disease and submaximal exercise heart rate response

Purpose: The safety of regadenoson (Reg) during low-level exercise testing has been established. However, its administration at peak exercise for patients who do not reach target heart rate (THR) on standard exercise treadmill stress testing (ETT) needs to be established, particularly among patients with known coronary artery disease (CAD) Methods: From our stress myocardial perfusion imaging (MPI) database, we identified all patients between 2009 and 2012 who underwent standard ETT and received Reg at peak exercise for failure to reach THR. Hemodynamics, side effects, and adverse events were entered prospectively into the database at the time of testing and were subsequently retrieved for analysis. Results: There were 514 patients, mean age 60 ± 12 years, 34 % female gender, and 51 % with prior CAD. There were 218 (42 %) and 297 (57 %) patients who underwent standard or modified Bruce and Cornell protocols, respectively, and with a mean exercise time of 5.8 ± 2.1 min. The mean percentage of peak heart rate achieved was 71 ± 8 %, and mean maximal metabolic equivalent (MET) was 6.7 ± 1.8. There were 63 (12 %) patients who developed ≥30 mmHg drop in systolic blood pressure (SBP) after 2 min of Reg administration, and 10 (2 %) had SBP <100 mmHg at 2 min and were younger and achieved higher METs; 8 and 2 patients were symptomatic, respectively. The most common side effects reported were shortness of breath (12 %), chest pain/discomfort (13 %), and dizziness (7 %). There was one syncopal event, but no high-degree heart block, cardiac or respiratory arrest. Four patients received aminophylline. Women were more likely to have shortness of breath or gastrointestinal symptoms, while diabetics were less likely to have chest discomfort. There was otherwise no significant difference in adverse events between different groups including those with and without CAD. Conclusion: Among patients undergoing standard treadmill stress testing for MPI who do not reach THR, the administration of Reg at peak exercise is safe and without major adverse events. Future large prospective studies are warranted to further evaluate the off-label use of Reg in this setting.