The goal of this study is to evaluate the diagnostic accuracy of a novel plaque-based coronary CT angiography (CCTA) fractional flow reserve (FFRct) software device for the estimation of invasive fractional flow reserve (FFR).

Researchers will compare the Elucid plaque-based FFRct analysis to invasively measured FFR in patients who have previously undergone CCTA and invasively assessed FFR.

Invasive fractional flow reserve is a clinically validated measure of lesion-specific ischemia and is preferred over visual estimation of diameter stenosis for clinical decision-making regarding coronary revascularization in patients with stable clinical presentations. Fractional flow reserve derived from coronary computed tomography angiography (FFRct) using computational fluid dynamic (CFD)-based software has been shown to be a reasonably accurate estimate of invasive FFR and is included in contemporary guidelines as a decision-tool for management of patients with intermediate stenosis on CCTA. However, CFD-based FFRct is calculated based predominately on detailed coronary lumen geometry. It is understood that the burden and type of coronary atherosclerosis, in addition to lumen geometry, significantly impacts the vasodilatory capacity of the coronary endothelium.

Preliminary studies suggest that invasive FFR can be accurately estimated based on the quantification of coronary plaque burden and the assessment of plaque composition. Previously, the investigators have demonstrated that a novel plaque-based FFRct approach, using a histologically validated software (ElucidVivoTM) for the measurement of plaque morphology (volume, plaque risk characteristics, and stenosis) to train a deep-learning model, was shown to be accurate and superior to lumen stenosis for predicting invasive FFR in a single-site feasibility study.

In this study, the investigators seek to assess the diagnostic accuracy of the Elucid plaque-based FFRct software to estimate invasive FFR in patients at multiple centers.

Inclusion Criteria:

- Adults >=18 years with at least one 30-90% stenosis on CCTA (>64- detector row) performed within 60 days of undergoing invasive FFR.

Exclusion Criteria:

• History of coronary revascularization with coronary artery bypass graft (CABG) surgery and/or percutaneous coronary intervention (PCI) (stent or balloon angioplasty) prior to CCTA and invasive FFR.
• History of myocardial infarction prior to CCTA and invasive FFR.
• Known complex congenital heart disease.
• Existing pacemaker or internal defibrillator lead implantation(s).
• Existing prosthetic heart valve.
• Absence of CCTA Digital Imaging and Communications in Medicine (DICOM) data for analysis.
• Absence of invasive coronary angiography imaging or adequate description defining the position of the invasive FFR wire location.
• Poor CCTA image quality that does not meet Elucid image processing requirements for plaque and FFRct.
• Absence of study date for CCTA or invasive FFR.
• Interval clinical myocardial infarction, diagnosis of decompensated heart failure, stroke, or coronary revascularization procedure between CCTA and invasive FFR.
• Non-diagnostic CCTA or invasive FFR. Studies where the results of the study were deemed non-diagnostic for clinical decision-making will be excluded.
• CCTA or invasive FFR studies performed prior to 1 January 2016.

Adults >=18 years with at least one 30-90% stenosis on CCTA (>64- detector row) performed within 60 days of undergoing invasive FFR.