Study of the Safety and Efficacy of Apadenoson for Detection of Myocardial Perfusion Defects Using SPECT MPI

The purpose of this study is to see whether apadenoson is as effective as adenosine when used as a pharmacological stress agent in myocardial SPECT-imaging (SPECT-MPI)to detect defects in the supply of blood to the heart muscle (myocardial perfusion defects). The study will also look at whether apadenoson is better tolerated than adenosine when used in SPECT-MPI.