This trial evaluates the effects of Empagliflozin versus Sitagliptin, in addition to standard of care, on global myocardial perfusion reserve using dynamic single-photon emission computed tomography (SPECT) images.

Inclusion Criteria:

• Men or women at least 19 years of age
• Type 2 diabetes mellitus
• Stable coronary artery disease
• Global myocardial perfusion reserve (MPR) index < 2.5
• The patient or guardian agrees to the study protocol and the schedule of clinical and dynamic SPECT follow-up, and provides informed, written consent, as approved by the appropriate Institutional Review Board/Ethical Committee of the respective clinical site.

Exclusion Criteria:

• Contraindications to empagliflozin, Sitagliptin
• DPP4 inhibitors or Sodium-glucose cotransporter-2(SGLT2) inhibitors within the previous 4 weeks
• Insulin requiring diabetes
• Poor glucose control (HbA1C>10 %)
• Acute coronary syndrome
• Stent placement within the previous 6 months
• Previous coronary artery bypass graft surgery within the previous 6 months
• Planned revascularization within 6 months
• Heart failure requiring loop diuretics
• Severe left ventricular hypertrophy (left ventricular septal wall thickness > 13mm)
• Significant renal disease manifested by creatinine clearance of < 30 ml/min)
• Hepatic disease or biliary tract obstruction, or significant hepatic enzyme elevation (alanine transaminase or Aspartate Aminotransferase > 3 times upper limit of normal)
• Radiopaque material implanted in the chest wall (metal, silicone, etc.)
• Contraindication to adenosine stress test
• Any clinically significant abnormality identified at the screening visit, physical examination, laboratory tests, or electrocardiogram which, in the judgment of the Investigator, would preclude safe completion of the study.
• Patient's pregnant or breast-feeding or child-bearing potential
• Expected life expectancy < 1 year
• Unwillingness or inability to comply with the procedures described in this protocol