Optimal Cutoff Value of Fractional Flow Reserve Derived From Coronary Computed Tomography Angiography for Predicting Hemodynamically Significant Coronary Artery Disease

Background: The optimal cutoff value of fractional flow reserve (FFR) derived from coronary computed tomography angiography (FFR CT ) remains unclear. Methods: The current study population consisted of 93 patients with 139 vessels, who had suspected coronary artery disease by computed tomography angiography and underwent invasive FFR. We evaluated diagnostic performance of FFR CT according to different FFR CT cutoff values and FFR CT ranges with invasive FFR ≤0.80 as the reference standard. Results: In per-vessel analysis, median invasive FFR was 0.85 (interquartile range, 0.75–0.90), and 57 out of 139 vessels (41%) showed hemodynamically significant stenosis (≤0.80). Median FFR CT was 0.77 (interquartile range, 0.66–0.84; mean difference [invasive FFR-FFR CT ], 0.06±0.11). Per-vessel accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 73%, 95%, 59%, 61%, and 94% for the cutoff value of FFR CT ≤0.80, 81%, 86%, 78%, 73%, and 89% for FFR CT ≤0.75, and 83%, 74%, 89%, 82%, and 83% for FFR CT ≤0.70, respectively. Per-vessel accuracy across the different ranges of FFR CT ≤0.60, 0.61 to 0.70, 0.71 to 0.80, 0.81 to 0.90, and >0.90 with the cutoff value of FFR CT ≤0.80 were 95%, 74%, 32%, 93%, and 100%, respectively. Setting a gray zone of FFR CT 0.71 to 0.80 provided high positive predictive value (82%; n=42/51) in the range of FFR CT ≤0.70 and high negative predictive value (94%; n=48/51) in FFR CT >0.80. Conclusions: This study suggested that referral to invasive coronary angiography should be considered individually in the range of FFR CT 0.71 to 0.80, whereas dichotomous decision could be made in FFR CT ≤0.70 and >0.80. Future prospective studies evaluating clinical outcomes are needed to establish optimal FFR CT -based diagnostic algorithm.