 ADVANCE MPI 2 is a multi-national, double-blind, randomized, active-controlled, parallel group clinical trial to evaluate the safety and efficacy of regadenoson in SPECT MPI compared to that of the approved pharmacological stress agent, Adenoscan. Patients referred for a clinically indicated pharmacological stress MPI study will be eligible for enrollment. The trial is designed: 1 to compare the pharmacological stress SPECT images obtained with regadenoson to those obtained with Adenoscan, and 2 to compare the safety and tolerability of the two stress agents. 