Velocity vector comparison between vector flow imaging and computational fluid dynamics in the carotid bifurcation

Implanted blood vessel external support device for the treatment of distal hypoperfusion ischemic syndrome in arteriovenous fistulas and high-frame-rate Vector Flow quality assessment

INTRODUCTION

Distal hypoperfusion ischemic syndrome (DHIS) is a complication occurring after arteriovenous fistula (AVF) creation. Different surgical alternatives haves been proposed in case of severe DHIS. Aim of the present paper is to present a new technique for DHIS treatment.

MATERIAL AND METHODS

Between the 1st of January 2021 and the 31st December 2021 all the patients referred to our center for DHIS grade 2-4 were treated with a new surgical technique. It consists of AVF remodeling using an external nitinol support (VasQ®) to reduce the risk of outflow vein enlargement and DHIS recurrence. To better appreciate the hemodynamic effects of the surgery, a new ultrasound technique called high-frame-rate Vector Flow (HiFR-VF) was used.

RESULTS

Seven patients (M:F 1:3; mean age 43 ± 12 years, range 29-65) were included in this study. Central line was never necessary, and technical success was 100% at 12 months. The comparison with historical data demonstrated lower recurrence of symptoms in comparison to simple artery-to-vein redo (p 0.50). The HiFR-VF showed flow with limited turbulent characteristics at the anastomosis site.

DISCUSSION AND CONCLUSION

The new technique proposed demonstrated to be safe and effective for treatment of DHIS, preventing symptoms recurrence. Ultrasound examination and HiFR-VF can be considered a valuable method to evaluate complex flows at the levels of vascular anastomosis.

Detection of Abnormal Wall Shear Stress and Oscillatory Shear Index via Ultrasound Vector Flow Imaging as Possible Indicators for Arteriovenous Fistula Stenosis in Hemodialysis

OBJECTIVE

The arteriovenous fistula (AVF) is an essential vascular access for hemodialysis patients. AVF stenosis may occur at sites with abnormal wall shear stress (WSS) and oscillatory shear index (OSI), which are caused by the complex flow in the AVF. At present, an effective method for rapid determination of the WSS and OSI of the AVF is lacking. The objective of this study was to apply an ultrasound-based method for determination of the WSS and OSI to explore the risk sites of the AVF.

METHODS

In this study, the ultrasound vector flow imaging technique V Flow was applied to measure the WSS and OSI at four different regions of the AVF to detect and analyze the risk sites: (i) anastomosis region, (ii) curved region, (iii) proximal vein and (iv) distal vein. Twenty-one patients were included in this study. The relative residence time was calculated based on the measured WSS and OSI.

RESULTS

The curved region had the lowest WSS; the anastomosis region had a significantly higher OSI (p < 0.05) compared with the venous regions, and the curved region had a significantly higher RRT (p < 0.05) compared with the proximal vein region.

CONCLUSION

V Flow is a feasible tool for studying WSS variations in AVF. The possible risk site in the AVF may be located in the anastomosis and curved regions, where the latter could present a higher risk for AVF stenosis.