EuroIntervention 2020;15: e 1594- e 1601 published online September 2019 published online e -edition April 2020 DOI: 10.4244/EIJ-D-18-01165 e 1594 CORONARY INTERVENTIONS CLINICAL RESEARCH © Europa Digital & Publishing 2020. All rights reserved. *Corresponding author: Hospital Clínico San Carlos, Calle del Prof Martín Lagos, s/n, 28040 Madrid, Spain. E-mail: escaned@secardiologia.es Angiography-derived functional assessment of non-culprit coronary stenoses in primary percutaneous coronary intervention Francesco Maria Lauri 1 , MD; Fernando Macaya 1 , MD; Hernán Mejía-Rentería 1 , MD; Sonoka Goto 1 , MD; Julian Yeoh 2 , MBBS, FRACP; Masafumi Nakayama 3 , MD, PhD; Alicia Quirós 4 , PhD; Catherine Liontou 1 , MD, PhD; Nilesh Pareek 2 , MA, MBBS; Antonio Fernández-Ortíz 1 , MD, PhD; Carlos Macaya 1 , MD; Philip MacCarthy 2 , MBChB, PhD; Javier Escaned 1 *, MD, PhD 1. Hospital Clinico San Carlos IDISSC and Complutense University of Madrid, Madrid, Spain; 2. King’s College Hospital, London, United Kingdom; 3. Toda Chuo General Hospital, Toda, Japan; 4. Department of Mathematics, Universidad de León, Leon, Spain F.M. Lauri and F. Macaya made equal contributions to the present work. A list of the study collaborators can be found in the Appendix paragraph. This paper also includes supplementary data published online at: https://eurointervention.pcronline.com/doi/10.4244/EIJ-D-18-01165 Abstract Aims: Functional assessment of non-culprit lesions (NCL) in patients presenting with ST-elevation myo- cardial infarction (STEMI) and multivessel disease constitutes an unmet need. This study aimed to evaluate the diagnostic accuracy of quantitative flow ratio (QFR) in the functional assessment of NCL during the acute phase of STEMI. Methods and results: This was a retrospective, observational, multicentre study including patients with STEMI and staged fractional flow reserve (FFR) assessment of NCL. QFR in NCL was calculated from the coronary angiogram acquired during primary PCI in a blinded fashion with respect to FFR. The diagnostic value of QFR in the STEMI population was compared with a propensity score-matched population of sta- ble angina patients. Eighty-two patients (91 NCL) were included. Target lesions were of both angiographic and functional (mean FFR 0.82±0.09) intermediate severity. The diagnostic performance of QFR was high (AUC 0.91 [95% CI: 0.85-0.97]) and similar to that observed in the matched control population (AUC 0.91 vs 0.94, p=0.5). The diagnostic accuracy of QFR was very high (>95%) in those vessels (61.5%) with QFR values out of a ROC-defined “grey zone” (0.75-0.85). A hybrid FFR/QFR approach (FFR only when QFR is in the grey zone) would adequately classify 96.7% of NCL, avoiding 58.5% of repeat diagnostic procedures. Conclusions: QFR has a good diagnostic accuracy in assessing the functional relevance of NCL during primary PCI, similar to the accuracy observed in stable patients. KEYWORDS • coronary artery disease • fractional flow reserve • non-invasive imaging • STEMI SUBMITTED ON 07/12/2018 - REVISION RECEIVED ON 1 st 15/04/2019 / 2 nd 16/08/2019 / 3 rd 16/09/2019 - ACCEPTED ON 18/09/2019