888 THE USE OF QFR FOR THE FUNCTIONAL ASSESSMENT OF EXTRACRANIAL INTERNAL CAROTID ARTERY STENOSIS

Abstract

Background
In asymptomatic patients with haemodynamically significant internal carotid artery stenosis, if endarterectomy cannot be considered, a selective invasive angiography is indicated before deciding for percutaneous revascularization. Sometimes, the angiographic assessment of the stenosis might be discordant with the non-invasive assessment, usually performed with Doppler. Therefore, the use of an angiography-based method that allows a functional assessment of the stenosis could be useful to help the diagnostic-therapeutic process. The aim of this study was to evaluate the diagnostic accuracy of Quantitative Flow Ratio (QFR) in the assessment of extracranial internal carotid artery stenosis.

Materials and methods
This registry prospectively enrolled asymptomatic patients with an indication to perform a selective angiography of the supra-aortic trunks. The systolic peak velocity obtained by colour Doppler ultrasound was used to determine the hemodynamic significance of the carotid stenosis (PSV> 120 cm / sec), whereas it was defined angiographically significant a stenosis with a %DS > 60%, according to NASCET criteria (%DSNASCET). After three-dimensional reconstruction of the angiographic data, QFR, Area Stenosis (AS%) and the minimum luminal area (MLA, mm2) were obtained.

Results
30 consecutive patients were enrolled, and 60 carotid arteries analysed, 8 of which were excluded because of previous percutaneous (n = 3) or surgical (n = 5) revascularization. On linear regression analysis, an inverse linear correlation was observed between QFR and PSV values (r2 = 0.71, p <0.001) and% DSNASCET (r2 = 0.79, p <0.001) (Figure 1). Similarly, the MLA values showed a significant correlation with both PSV and% DSNASCET (respectively, r2 = 0.67 and r2 = 0.75, p <0.001), as well as AS values, which also showed a significant correlation with both PSV and% DSNASCET (respectively, r2 = 0.68 and r2 = 0.88, p <0.001). The QFR and the% DSNASCET showed a comparable and high diagnostic accuracy (AUC = 0.99, p <0.001) using PSV as a reference, with a cut-off value of 0.95 for the QFR (Figure 2). However, considering the% DSNASCET cut-off values, the QFR showed higher diagnostic accuracy, sensitivity and negative predictive value as compared with % DSNASCET.

Conclusions
This study showed the feasibility of QFR for the assessment of extracranial internal carotid artery stenosis. It was effective indeed for predicting the functional significance of the stenosis considering the Doppler as standard of reference. However, whether revascularization of the carotid stenosis should be guided by QFR rather than the angiography alone has still to be evaluated.