Diagnostic performance of on-site CT-derived fractional flow reserve versus CT perfusion

To compare the diagnostic accuracy of on-site computed tomography (CT)-derived fractional flow reserve (FFR) and stress CT myocardial perfusion (CTP) in patients with coronary artery disease. Using a prospective CTP registry, 72 patients with invasive FFR were enrolled. CT-derived FFR was computed on-site using rest-phase CTP data. The diagnostic accuracies of coronary CT angiography (CCTA), CT-derived FFR, and stress CTP were evaluated using an area under the receiver-operating characteristic curve (AUC) with invasive FFR as a reference standard. Logistic regression and the net reclassification index (NRI) were used to evaluate incremental differences in CT-derived FFR or CTP compared with CCTA alone. The per-vessel prevalence of haemodynamically significant stenosis (FFR ≤ 0.80) was 39% (54/138). Per-vessel sensitivity and specificity were 94 and 66% for CCTA, 87 and 77% for CT-derived FFR, and 79 and 91% for CTP, respectively. There was no significant difference in the AUC values of CT-derived FFR and CTP (P = 0.845). The diagnostic performance of CCTA (AUC = 0.856) was improved by combining it with CT-derived FFR (AUC = 0.919, P = 0.004, NRI = 1.01) or CTP (AUC = 0.913, P = 0.004, NRI = 0.66). CT-derived FFR values had a moderate correlation with invasive FFR (r = 0.671, P < 0.001). On-site CT-derived FFR combined with CCTA provides an incremental diagnostic improvement over CCTA alone in identifying haemodynamically significant stenosis defined by invasive FFR, with a diagnostic accuracy comparable with CTP.