IRB Approval expired on 05/28/09 as it was pilot study. A new study was later initiated once VA Merit Review Grant (I01CX000342-01) was received. Thus a new IRB (10-05-05-02) and clinicaltrials.gov (NCT01719016) were initiated in place of this study.

Newly developed diagnostic parameters have potential to differentiate between epicardial disease and microvascular dysfunction with the help of anatomical details and physiological endpoints and can be used in present clinical settings.

The pressure drop coefficient (CDP) is a functional index based on hyperemic dp and u measurements. The lesion flow coefficient (LFC) combines the functional index CDP with an atomic measure (percentage area stenosis) as a single parameter.

Inclusion Criteria:

• Abnormal Myocardial stress perfusion (SPECT) LV EF > 25%
• 18 years of age or above
• Patients referred to a stress test by a Cardiologist
• Acute Chest pain, as per patient input.
• Risk Assessment with prior test results and/or previous history of known chronic stable CAD.
• Borderline or discordant stress testing where obstructive CAD remains a concern.
• New or worsening symptoms- Abnormal coronary angiography or abnormal prior stress imaging study.
• Coronary stenosis or anatomic abnormality of uncertain significance.
• In absence of reliable diagnostic information from another imaging modality.

Exclusion Criteria:

• Serum Creatinine > 2.5 gm/dL
• Type II HIT
• Left ventricular ejection fraction less the 25% determined by gated SPECT imaging ( - LV < or + to 25%)
• Non-dialysis dependent chronic kidney disease with baseline serum creatinine greater than 2.5 gm/dL.
• History of type II heparin-induced thrombocytopenia.
• Significant co-morbid condition that is medically unstable and would make coronary angiography prohibitive or contraindicated.
• Pregnant women.
• Incapacitated for Consent

Patients with chest pain and suspected ischemia that needs to be assessed by a stress test