Regadenoson, a Novel Pharmacologic Stress Agent for Use in Myocardial Perfusion Imaging, Does Not Have a Direct Effect on the QT Interval in Conscious Dogs

Our goal was to determine the effect of regadenoson (a novel A(2A) adenosine receptor agonist) on the QT interval in conscious dogs. Sixteen mongrel dogs were chronically instrumented for measurements of blood pressure and ECG. Regadenoson (2.5, 5, and 10 mu g/kg, IV) caused a dose-dependent QT interval shortening (Delta QT: 14 +/- 3, 24 +/- 5, and 27 +/- 5 ms, mean +/- SEM; n = 7 to 11; all P < 0.05) associated with significant increases in HR (Peak HR: 114 9, 125 +/- 6, and 144 +/- 7 bpm). Atrial pacing (135, 150, and 165 bpm) also caused a frequency-dependent shortening of the QT interval (Delta QT: 15 +/- 3, 22 +/- 3, and 39 +/- 5 ms; n = 6 to 7; all P < 0.05). Regadenoson- and pacing-induced shortenings in the QT interval were significantly correlated with the R-R interval (r = 0.67 and 0.8, both P < 0.05). Regadenoson at 5 and 10 mu g/kg did not cause a significant change in H R or QT interval either during aerial pacing at 165 bpm or after administration of propranolol and atropine to prevent HR from changing or after treatment of dogs with hexamethonium to block autonomic ganglia. Regadenoson (5 to 10 mu g/kg) caused no significant changes of QT interval in the heart in which HR was kept constant via physiological or pharmacological procedures, indicating that regadenoson has no direct effect on the QT interval.