Due to nationwide shortage of Aminophylline. No subjects enrolled.

The investigators developed a modified regadenoson nuclear stress test of the heart that incorporates an aminophylline injection following regadenoson (The ASSUAGE protocol). The modified (ASSUAGE) protocol has been associated with fewer side effects and was better tolerated by patients.

This study will investigate whether the modified regadenoson stress protocol (ASSUAGE) produces blood flow pattern to the heart similar to that of a standard regadenoson stress protocol. In proven to be the case, the ASSUAGE protocol has the potential to be used on a wide scale instead of the current standard protocol.

Patients who had regadenoson stress nuclear stress test of the heart will be invited to return to undergo a modified nuclear stress using the modified (ASSUAGE) protocol. Images from the original scan will be compared to those from the second scan to determine whether the blood flow pattern is similar between the two scans.

Inclusion Criteria:

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

Exclusion Criteria:

• 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