Evaluation of epicardial coronary resistance using computed tomography angiography. A Proof Concept

AIMS: Fractional flow reserve (FFR) pullback allows to assess the distribution of pressure loss along the coronary vessels. FFR derived from CT (FFRCT) provides a virtual pullback curve that may also aid in the assessment of the distribution of epicardial coronary resistance in the non-invasive setting. The present study aims to determine the accuracy of the virtual FFRCT pullback curve using a motorized invasive FFR pullback as reference in patients with stable coronary artery disease. METHODS AND RESULTS: FFR values were extracted from coronary vessels at approximately 1 mm to generate pullback curves. Invasive motorized FFR pullbacks were acquired using a dedicated device at a speed of 1 mm/s. A total of 3172 matched FFRCT and FFR values were obtained in 24 vessels. The correlation coefficient between FFRCT and FFR was 0.76 (95%CI 0.75 to 0.78; p < 0.001). The area under the pullback curve was similar between FFRCT and invasive FFR (79.0 ± 16.1 vs. 85.3 ± 16.4, p = 0.097). The mean difference in lesion gradient between FFRCT and FFR was -0.07 (LOA -0.26 to 0.13) whereas in non-obstructive segments was -0.01 (LOA -0.06 to 0.05). CONCLUSION: The evaluation of epicardial coronary resistance using coronary CT angiography with FFRCT was feasible. FFRCT virtual pullback appears to be accurate for the evaluation of pressure gradients. FFRCT has the potential to identify the pathophysiological pattern of coronary artery disease in the non-invasive setting.