Diagnostic performance of on-site, CT-derived fractional flow reserve in predicting invasive fractional flow reserve and absolute myocardial blood flow

Background CT-derived fractional flow reserve (FFR) improves the diagnostic accuracy of coronary CT angiography (CCTA) but typically requires off-site processing. We evaluated the agreement and diagnostic accuracy of a fast (∼8-min), on-site CT-FFR algorithm against invasive FFR and its correlation with myocardial blood flow. Methods and results Patients with suspected chronic coronary syndrome and at least one ≥50 ​% diameter stenosis on CCTA underwent [ 15 O]H 2 O PET and invasive coronary angiography with three-vessel invasive FFR. Thirty-eight patients with 89 vessels were included for analysis. Median invasive and CT-FFR were 0.92 (IQR 0.80–0.97) and 0.84 (IQR 0.68–0.91), respectively (rho ​= ​0.75). Against invasive FFR ≤0.80 on a per-patient level, CT-FFR ≤0.80 showed 84 ​% accuracy (95 ​% CI 70–93 ​%), 100 ​% sensitivity (95 ​% CI 85–100 ​%), 62 ​% specificity (95 ​% CI 39–82 ​%), a positive predictive value (PPV) of 79 ​% (95 ​% CI 60–90 ​%), negative predictive value (NPV) of 100 ​% (95 ​% CI 72–100 ​%). Compared with ≥50 ​% diameter stenosis on CCTA on a per-vessel level, CT-FFR ≤0.80 had similar sensitivity and NPV but higher accuracy, specificity, and PPV. Both CT-FFR and invasive FFR correlated weakly with stress myocardial blood flow (rho 0.30 and 0.35, respectively) and myocardial flow reserve (rho 0.20 and 0.38, respectively). Conclusion A novel on-site CT-FFR algorithm demonstrates fast and very high rule-out capability and incremental rule-in potential beyond diameter stenosis for functionally significant disease determined by invasive FFR in patients with suspected stenosis at CCTA. Both measures of FFR correlated weakly with myocardial blood flow and flow reserve by [ 15 O]H 2 O PET.