Patients who are previously scheduled for diagnostic coronary angiography will be approached for consent to be part of the study. If the patient is found to have one or two vessel disease and it is planned by the interventional cardiologist that FFR will be used, then the previously consented patient will be deemed appropriate for the study. The standard procedure will be followed for FFR testing using regadenoson. The patient will then receive the standard dose of Tc-99m sestamibi. The interventional cardiologist will proceed with percutaneous coronary intervention (PCI) if appropriate. Patients will proceed to the cardiac catheterization laboratory holding area post procedure. Patients will then be scheduled to be taken to the nuclear cardiology laboratory one to three hours following the coronary angiogram for standard SPECT acquisition. Patients will be monitored for 2-6 hours or overnight as clinically indicated following diagnostic coronary angiography and PCI. Low dose resting myocardial perfusion scanning may be performed the next day if stress myocardial perfusion study was abnormal.