Diagnostic performance of transluminal attenuation gradient and fractional flow reserve by coronary computed tomographic angiography (FFRCT) compared to invasive FFR: a sub-group analysis from the DISCOVER-FLOW and DeFACTO studies

Although coronary computed tomographic angiography (CCTA) has been a robust diagnostic tool to identify anatomical significance of coronary artery disease (CAD), the utility of CCTA to assess hemodynamic significance of CAD remains unclear. We investigated the diagnostic performance of transluminal attenuation gradient (TAG) and fractional flow reserve derived from CCTA (FFRCT) to predict lesion-specific ischemia by invasive FFR. We identified 103 patients with suspected or known CAD enrolled from the DISCOVER-FLOW and DeFACTO studies who underwent invasive coronary angiography with FFR and high quality a parts per thousand yen64-slice CCTA. Diagnostic performance for predicting abnormal invasive FFR (a parts per thousand currency sign0.80) was assessed for TAG [a parts per thousand currency signa'1.1 HU/mm by the area under the curve (AUC) by receiver-operating characteristic curve analysis (ROC)], FFRCT (a parts per thousand currency sign0.80), and CCTA stenosis (a parts per thousand yen50 %). On a per-vessel analysis (n = 146), 52 vessels (35.6 %) had ischemia by invasive FFR. The sensitivity, specificity, positive predictive value and negative predictive value were 53.8, 45.7, 35.4, 64.2 % for TAG, 82.7, 74.5, 64.2, 88.6 % for FFRCT, 84.6, 39.4, 43.6, 82.2 % for CCTA stenosis, respectively. The AUC by ROC curve analysis for FFRCT (0.79) demonstrated greater discrimination of hemodynamic ischemia compared to TAG (0.50, p < 0.0001 vs. FFRCT), CCTA stenosis (0.62, p = 0.0004 vs. FFRCT) and the combination of the two (0.63, p = 0.004 vs. FFRCT). These results remained consistent regardless of the number of CCTA slices. FFRCT allows identification of lesion-specific ischemia using invasive FFR as a reference standard with greater diagnostic accuracy than TAG, CCTA stenosis, or the combination of the two.