Advanced Ultrasound Applications for Predicting AVF Outcomes

Overview

Haemodialysis is a renal replacement therapy that can be introduced to patients with end-stage renal disease (ESRD) to help them maintain a good healthy life. The patient's blood is pumped through a dialysis machine to remove excess fluid, salt and waste, then it is pumped back into the patient's circulation system. In order to carry out haemodialysis, vascular access (VA) is required to connect the patient to the dialysis machine. Patients have only three options of vascular access: arteriovenous fistula (AVF), an anastomosis between a native vein and an artery; arteriovenous graft (AVG), a connection between a synthetic tube and native blood vessels; and (3) central line, a cuffed catheter placed in a large neck vein. Arteriovenous fistulas are the preferred method for VA because of their longevity and causing the least number of complications. Although there are a number of factors that may increase the probability of AVF failure rate such as age and gender of the patient, poor native vessel structure, medications and the level of surgical experience, 30-40% of new AVFs fail to mature for unknown reasons. For an AVF to become functionally mature postoperative, remodelling and dilation of the native artery and vein are essential to accommodate significantly increased blood flow. However, pre-existing diseases in patients with ESRD such as arterial stiffness and endothelial dysfunction may impair AVF and preclude dialysis. It has been asserted that the lack of AVF success is attributable to insufficient arterial dilation because of poor arterial wall elasticity. The study aims to investigate the role of arterial stiffness and endothelial dysfunction in predicting AVF outcome using novel non-invasive ultrasound applications: 2D shear wave elastography and 2D strain speckle tracking will be employed to assess arterial stiffness, while an intraoperative flow-mediated dilation (FMD) technique will be used to evaluate endothelial dysfunction.

This is an observational prospective pilot study of patients with end-stage renal disease (ESRD), who will be referred for AVF procedure. Duration: 21 Months The research team will collect data from the patients after they have signed the informed consent form. Data collection will take place before, during and after arteriovenous fistula (AVF) surgery. At 0 week, the patient will be interviewed to obtain clinical information. Also, blood pressure and body mass index will be checked and recorded. Next, pre-operative AVF assessment ultrasound measurements will be performed to assess flow, pulsatility and vessel diameter. Advanced ultrasound applications(2D strain speckle tracking and 2D Shear wave elastography) will be applied to assess arterial stiffness as additional measurement tools. These are quantitative measures of vessel stiffness. It takes less than five minutes to obtain these measurements from the imaged vessel. During AVF surgery, the endothelial function will be assessed intraoperatively by testing the ability of the endothelium to dilate, flow mediation dilation (FMD). Leftover vessel specimens will be collected for histopathological analysis purpose. At 6 week, post-AVF ultrasound assessment will be conducted to assess the maturation of AVF by measuring ultrasound parameters of blood flow, pulsatility and vessel diameter. Arterial stiffness parameters will be measured as well. Blood pressure and BMI will be assessed and recorded. Study data will be entered into a study database which will consist of a password encrypted stored on a password-protected computer in the vascular lab at Hammersmith Hospital. Only the study researchers will know the study database password. Data analysis will be performed after the enrolment of 20, 40 and 75 patients.