The reliability and utility of on-site CT-derived fractional flow reserve (FFR) based on fluid structure interactions: comparison with FFR_CT based on computational fluid dynamics, invasive FFR, and resting full-cycle ratio

Fractional flow reserve (FFR) derived off-site by coronary computed tomography angiography (CCTA) (FFR_CT) is obtained by applying the principles of computational fluid dynamics. This study aimed to validate the overall reliability of on-site CCTA-derived FFR based on fluid structure interactions (CT-FFR) and assess its clinical utility compared with FFR_CT, invasive FFR, and resting full-cycle ratio (RFR). We calculated the CT-FFR for 924 coronary vessels in 308 patients who underwent CCTA for clinically suspected coronary artery disease. Of these patients, 35 patients with at least one obstructive stenosis (> 50%) detected on CCTA underwent both CT-FFR and FFR_CT for further investigation. Furthermore, 24 and 20 patients underwent invasive FFR and RFR in addition to CT-FFR, respectively. The inter-observer correlation (r) of CT-FFR was 0.93 (95% confidence interval [CI] 0.85–0.97, P < 0.0001) with a mean absolute difference of − 0.0042 (limits of agreement − 0.073, 0.064); 97.3% of coronary arteries without obstructive lesions on CCTA had negative results for ischemia on CT-FFR (> 0.80). The correlation coefficient between CT-FFR and FFR_CT for 105 coronary vessels was 0.87 (95% CI 0.82–0.91, P < 0.0001) with a mean absolute difference of − 0.012 (limits of agreement − 0.12, 0.10). CT-FFR correlated well with both invasive FFR (r = 0.66, 95% CI 0.36–0.84, P = 0.0003) and RFR (r = 0.78, 95% CI 0.51–0.91, P < 0.0001). These data suggest that CT-FFR can potentially substitute for FFR_CT and correlates closely with invasive FFR and RFR with high reproducibility. Our findings should be proven by further clinical investigation in a larger cohort.