Background: Recently several publications described the diagnostic value of coronary CT angiography (coronary CTA) derived fractional flow reserve (CTA-FFR). For a recently introduced on-site CTA-FFR application, detailed methodology and factors potentially affecting performance have not yet been described.
Objective: To provide a methodological background for an on-site CTA-FFR application and evaluate the effect of patient and acquisition characteristics. Methods: The on-site CTA-FFR application utilized a reduced-order hybrid model applying pressure drop models within stenotic regions. In 116 patients and 203 vessels the diagnostic performance of CTA-FFR was investigated using invasive FFR measurements as a reference. The effect of several potentially relevant factors on CTA-FFR was investigated.
Results: 90 vessels (44%) had a hemodynamically relevant stenosis according to invasive FFR (threshold ≤0.80). The overall vessel-based sensitivity, specificity and accuracy of CTA-FFR were 88% (CI 95%:79-94%), 65% (55-73%) and 75% (69-81%). The specificity was significantly lower in the presence of misalignment artifacts (25%, CI: 6-57%). A non-significant reduction in specificity from 74% (60-85%) to 48% (26-70%) was found for higher coronary artery calcium scores. Left ventricular mass, diabetes mellitus and large vessel size increased the discrepancy between invasive FFR and CTA-FFR values.
Conclusions: On-site calculation of CTA-FFR can identify hemodynamically significant CAD with an overall per-vessel accuracy of 75% in comparison to invasive FFR. The diagnostic performance of CTA-FFR is negatively affected by misalignment artifacts. CTA-FFR is potentially affected by left ventricular mass, diabetes mellitus and vessel size.

Computational fluid dynamics, Coronary CT angiography, Diagnostic performance, Fractional flow reserve,
Journal of Cardiovascular Computed Tomography
Department of Radiology

Coenen, A, Lubbers, M.M, Kurata, A, Kono, A, Dedic, A, Chelu, R.G, … Nieman, K. (2016). Coronary CT angiography derived fractional flow reserve. Journal of Cardiovascular Computed Tomography, 10(2), 105–113. doi:10.1016/j.jcct.2015.12.006