Maximal Bruce Protocol With the Use of Regadenoson For Myocardial Perfusion Stress Testing

A nuclear stress test has been recommended for a patient by their doctor. This test helps to detect significant blockages in the artery to the heart. The test involves the patient walking on a treadmill until their heart rate reaches 85% of their age-determined maximal predicted heart rate. If the patient needs to stop walking for any reason (tiredness, chest pain, shortness of breath or dizziness) prior to reaching the 85% of their maximal heart rate, then the test becomes inaccurate and blockages can be missed. Nonetheless, the information that we gain from the patient walking remains valuable. If the subject does not reach 85%, the usual procedure is to re-do the test where the subject would not walk on the treadmill, but would be injected with a pharmacologic agent (drug) which dilates their blood vessels. This would allow us to obtain an accurate picture about any blockages in the blood vessels. By doing the "drug" test alone, we lose the important information gained by the treadmill test. In the present study the subject will be asked to walk on the treadmill and near the end of the walk, if they do not reach 85%, then the "drug" will be given to the patient. Regadenoson is FDA approved for drug stress testing. Regadenoson (versus one of the other pharmacological agents) will be given at a dose of 400 mcg, will be infused over 10 - 20 seconds followed by standard flushing solution, and then the infusion of a radiotracer (the FDA approved method of administration) will be given for nuclear imaging. The entire intravenous procedure takes 30 seconds. The subject will then undergo 5 minutes of standard observation/monitoring post infusion administration. Standard nuclear stress imaging will then follow. By doing this, we will obtain all the important information from the exercise portion of this test and maintain the accuracy to detect blockages. By doing the study in this manner, we will be able to save the subject time and obtain more information about the heart than either test individually.