Non-invasive instantaneous wave-free ratio using coronary CT angiography: diagnostic performance for evaluation of ischaemia-causing coronary stenosis confirmed by invasive fractional flow reserve

AIM: To determine the diagnostic performance of instantaneous wave-free ratio (iFR) derived from non-invasive coronary computed tomography angiography (CTA; iFR(CT)) for ischaemia-causing coronary stenosis, and to compare the diagnostic efficacy of iFR(CT), CTA, and CTA plus iFR(CT). METHODS AND MATERIALS: Thirty-nine patients (55 vessels) with known or suspected coronary artery disease were included. All patients underwent invasive coronary angiography and fractional flow reserve (FFR) according to CTA findings and clinical indicators. The same raw data used for CTA were used to build patient-specific computed flow dynamic models and to calculate iFR(CT). RESULTS: On a vessel-based level, the correlation between iFR(CT) and FFR was moderate (r=0.65, p<0.05); the optimal iFR(CT )cut-off value was 0.85 based on an FFR cut-off value of 0.80, resulting in 85% sensitivity, 69% specificity, 61% positive predictive value (PPV), 89% negative predictive value (NPV), and 75% accuracy. The AUC showed significant differences between iFR(CT) and CTA (vessel-based: 0.84 versus 0.68; patient-based: 0.84 versus 0.62; both p<0.01). The accuracy of CTA combined with iFR(CT) was significantly increased compared to CTA alone for vessels with intermediate stenosis (83% versus 40%, p<0.01). CONCLUSION: iFR(CT) showed better diagnostic performance than CTA. iFR(CT) may be a promising method for detection of ischaemia-causing coronary stenosis, even in vessels with intermediate stenosis. (C) 2018 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.