Assessment of renal artery stenosis using renal fractional flow reserve and correlation with angiography and color Doppler ultrasonography: data from FAIR-pilot trial

Renal fractional flow reserve (rFFR), a hemodynamic evaluation indicator for functional measurement, could be used for the detection of significant renal artery stenosis (RAS). In this study, we evaluated the correlation between color Doppler ultrasonography (CDU), angiography and rFFR in assessing RAS and to validate cut-off points of ultrasound parameters for significant RAS with rFFR<0.8. A total of 77 renal artery lesions from 58 patients with at least unilateral RAS were included into this study. All patients were participated in Fractional Flow Reserve to Determine the Appropriateness of Percutaneous Renal Artery Intervention in Atherosclerosis Renal Hypertension Patients (FAIR)-pilot study (NCT05732077). The rFFR was measured through a pressure wire after renal hyperemia induced by dopamine. Peak systolic velocity (PSV), renal-to-aortic ratio (RAR), resistive index (RI) and side-to-side differences of the intrarenal resistive indices (ΔRI) were obtained by CDU. The rFFR showed good correlation with both CDU and angiography assessment methods. Among CDU parameters, the best correlation was observed in rFFR with PSV (rho = −0.668, P < 0.0001) and RAR (rho = −0.597, P < 0.001). With a rFFR<0.80 as cut-off value for significant RAS, we computed sensitivity, specificity, and area under the curve (AUC) of CDU parameters. The most predicting cut-off points of CDU parameters were calculated as PSV for 2.415 m/s, RAR for 4.495, RI for 0.605 and ΔRI for 0.04, respectively. A PSV > 2.415 m/s provided a sensitivity of 90%, specificity of 75%, accuracy of 81% and AUC of 0.84 for detecting RAS with rFFR<0.8.