This study will evaluate the effectiveness of CorCTA by comparing the results of the test with another imaging method called Fractional Flow Reserve (FFR), which is done as a part of the cardiac catheterization.

Invasive X-ray coronary angiography remains the "reference standard" for the evaluation of coronary artery stenoses. Recently, coronary artery computed tomography angiography (CorCTA) has been introduced as a non-invasive method for the evaluation of coronary artery stenoses and has been shown to be highly accurate in stenosis detection when compared to invasive X-ray angiography. While invasive X-ray angiography and CorCTA evaluate morphological features of coronary arterial plaques, fractional flow reserve is an invasive measure of the hemodynamic significance of a stenosis obtained in the catheterization laboratory by measuring changes in intracoronary arterial pressure before and after maximal vasodilation induced by intracoronary adenosine. An FFR value less than 0.75 has been shown to predict ischemia in vascular beds distal to the stenosis by radionuclide perfusion modalities and has been shown to be associated with worse outcomes. Therefore, FFR is considered to be an invasive hemodynamic "reference standard" for the evaluation of the hemodynamic significance of coronary arterial stenoses. While intravascular ultrasound (IVUS) can provide additional morphological information in intermediate stenoses, it can not provide further functional information and cannot be used in more significant stenoses as the IVUS probe cannot be advanced through stenotic lesions.

We are currently conducting investigation in the validation of CorCTA against FFR in intermediate coronary artery stenoses (40-70%) (see below under "Preliminary Data"). However, CorCTA has not been validated against invasive hemodynamic measurements of fractional flow reserve in patients with stenoses >70% by invasive X-ray angiography. We hypothesize that CorCTA-derived measurements are accurate in the diagnosis of hemodynamically significant coronary artery stenoses, using FFR as the reference standard in patients with coronary artery stenoses>70%.

Inclusion Criteria:

• Age 21-85

• Presence of at least one obstructive coronary artery stenosis as defined by:

  • Previous catheterization or CT angiogram with any lesion 70% or greater
  • Previous positive functional stress test (this does not include CTA alone)

• Ability and Willingness to provide informed consent

• Ability and Willingness to perform required follow up procedures

Exclusion Criteria:

• History of coronary artery bypass graft surgery
• Previously revascularized lesion
• Creatinine>1.6 mg/dL or GFR<30 pre-procedure per institutional standards
• Known Pregnancy
• Inability to perform CTA
• Arrhythmia precluding diagnostic CT examination
• Contrast agent allergy that cannot be adequately premedicated
• Severe PVD precluding cardiac catheterization
• Patient not a candidate for IVUS and FFR
• Inability or unwillingness to provide informed consent
• Inability or unwillingness to perform required follow up procedures