Quantitative flow ratio for the functional assessment of extracranial internal carotid artery stenosis

Abstract

Abstract Background In asymptomatic patients at high surgical risk presenting with significant extracranial internal carotid artery stenoses, a selective invasive angiography is performed before carotid artery stenting (CAS). Sometimes, the angiographic findings of the stenosis could be discordant from those observed at the non-invasive imaging evaluation and the use of a pressure-wire to evaluate the hemodynamic potential of the stenosis, might be dangerous for the higher risk of cerebrovascular events. Purpose The Quantitative Flow Ratio (QFR), by estimating the contrast flow velocity and based on a 3-dimensional quantitative angiography, might be of value as an online angiography-based functional assessment of internal carotid stenoses, in order to guide the physicians in the decision-making process to proceed or not to revascularization. Methods We prospectively enrolled 14 asymptomatic patients with an indication for invasive treatment of internal carotid artery stenosis. The echo-colour-Doppler was performed in 28 vessels and the Peak Systolic Velocity (PSV, cm/sec) was used to identify functionally significant stenoses (PSV >120cm/sec). At the angiography, internal carotid artery stenosis degree was obtained according to NASCET criteria (%DSNASCET) and the lesion considered angiographically significant if >60%. After the exclusion of 4 vessels, QFR, Area Stenosis (AS, %) and Minimal Lumen Area (MLA, mm2) were obtained in the remaining 24 vessels (Figure 1, Panel A and B). Results At the linear regression analysis, QFR values significantly correlated with PSV (r2=0.71, p<0.001) as well as with %DSNASCET (r2=0.81, p<0.001). In addition, using the PSV as reference, QFR showed good accuracy to predict the presence of a functionally significant stenosis (AUC=1.00, p<0.001) with a cut-off value of 0.90. Similarly, the MLA significantly correlated with both the PSV and %DSNASCET (respectively, r2=0.61 and r2=0.60, p<0.001) as well as the AS (respectively, r2=0.68 and r2=0.87, p<0.001) (Figure 2). Conclusion This study suggests the possibility to adopt QFR for the functional assessment of extracranial internal carotid artery stenoses and should be considered as hypothesis generating to design a larger validation trial. Funding Acknowledgement Type of funding sources: None.