Assessment of renal artery stenosis using both resting pressures ratio and fractional flow reserve – Relationship to angiography and ultrasonography

Abstract

BACKGROUND. Clinical benefit from renal artery revascularization remains controversial, probably because of inaccurate stenosis severity assessment. Objective. The aim of the study was to evaluate resting translesional pressures ratio and renal fractional flow reserve (rFFR) in relation to angiography and Doppler duplex ultrasonography in patients with at least moderate renal artery stenosis (RAS). METHODS. 44 hypertensive patients (48% of males, mean age 65 years) with at least moderate RAS were investigated. Translesional systolic pressure gradient (TSPG), resting Pd/Pa ratio (the ratio of mean distal to lesion and mean proximal pressures) and hyperemic rFFR - after intrarenal administration of papaverine - were evaluated. Quantitative angiographic analysis of stenosis severity was performed including minimal lumen diameter (MLD) and percent diameter stenosis (DS) assessment. Renal/aortic ratio (RAR), resistive index (RI) and deltaRI (side-to side difference) were obtained in Doppler-duplex ultrasonography. The predictive value of selected variables was calculated using receiver-operating characteristics curves. RESULTS. Mean Pd/Pa ratio was 0.86 ± 0.12 and decreased to 0.79 ± 0.13 after papaverine administration. Both Pd/Pa ratio and rFFR strongly correlated with TSPG (r = -0.92, p < 0.0001 and r = -0.88, p < 0.0001, respectively) and moderately with MLD (r = 0.62, p < 0.0001 and r = 0.66, p < 0.0001) and DS (r = -0.63, p < 0.0001 and r = -0.70, p < 0.0001). To identify more than 70% RAS, considered severe, the most predictive cut-off values were 0.93 for Pd/Pa ratio and 0.80 for rFFR. CONCLUSIONS. Mean Pd/Pa ratio and rFFR strongly correlated with angiographic data and in less pronounced manner with ultrasound parameters reflecting intrarenal blood flow. The best accuracy cut-off points for severe RAS predicting were 0.93 and 0.80, respectively.

Renal Duplex Sonographic Evaluation of Type 2 Diabetic Patients

“…Moreover, advanced arteriosclerosis in intrarenal arteries at an advanced stage of diabetic nephropathy may contribute to the increase in the RI 48 . Therefore, renal hypertrophy and the increase in the RI could represent two different phases: renal enlargement is a prealbuminuric reversible step of renal involvement in diabetes mellitus, whereas the RI increase indicates the progression of disease with renal scarring, which precedes the appearance of albuminuria 49 – 52 …”

Duplex derived intrarenal resistance index correlates with invasive pressure gradient measurements in detecting relevant unilateral renal artery stenosis

“…For the fi rst time, a signifi cant correlation was found between a transstenotic pressure gradient ratio of < 0.90 as determined by pressure wire and a decrease in intrarenal RI < 0.05 when inducing RAS after stent placement by gradually infl ating a balloon catheter, as described by De Bruyne et al [15]. Kadziela et al [19] found that the mean transstenotic pressure gradient ratio and fractional fl ow reserve (FFR) strongly correlate with angiography and less so with ultrasound parameters. The best accuracy cut-off values for predicting severe RAS were a ratio of 0.93 and an FFR of 0.80.…”

Atherosclerotic renal artery stenosis is prevalent in cardiorenal patients but not associated with left ventricular function and myocardial fibrosis as assessed by cardiac magnetic resonance imaging

“…More recent PTA studies often combine this definition with additional haemodynamic measurements, e.g. a systolic pressure gradient [34], measurement of the fractional flow reserve [35] or use a more strict cut-point of >70%. In this study we used the definition of ARAS as defined >50%, in accordance with the STAR study [19].…”