Functional CT Assessment of Coronary Stenoses

Determining the hemodynamic impact of coronary artery stenoses has implications for patient management but conventional tools, e.g., diameter stenosis, are only modestly predictive. Fractional flow reserve (FFR) has been the gold standard adjudicator of hemodynamically significant coronary stenosis in the cardiac catheterization laboratory. Software algorithms utilizing models of computational flow dynamics have enabled FFR estimations obtained from static coronary CT angiography (CCTA) images. Optimal scan parameters including achieving an appropriate heart rate, vasodilation with nitroglycerin, and minimizing image noise and motion are necessary to ensure sufficient image quality for CT-derived FFR (CT-CT-FFR). CT-FFR must be interpreted in conjunction with CTA findings with attention to individual anatomic considerations. Lesion-specific values of <0.75 are considered hemodynamically significant, and values >0.8 are considered non-flow limiting, while values in the 0.75–0.80 range are intermediate, requiring further consideration of clinical and imaging factors. This chapter discusses concepts of functional assessment of coronary artery stenoses with CCTA as well as guidance for acquisition and interpretation.