patients who have had a qualifying regadenoson stress myocardial perfusion imaging (regadenoson nuclear stress test).

inability to provide an informed consent

known allergic reaction to aminophylline or regadenoson

systolic blood pressure < 90 mmhg

unstable abnormal heart rhythm

pulmonary edema

acute coronary symptoms, myocardial infarction within 48 hours

active dipyridamole, aminophylline or theophylline use

pregnancy

any contraindication to aminophylline according to the drug's package insert: uncontrolled seizure disorder, sepsis with multi-organ failure and liver impairment