AbstractThe arteriovenous fistula (AVF) is a lifeline for patients requiring renal replacement therapy, allowing repeated access to the high blood flow needed for haemodialysis. However, failure rates for AVFs remain high, at around 30-40 % after one-year, typically occluding secondary to stenosis. Many risk-factors for AVF failure have been identified, such as diabetes, age, gender and pre-operative vessel diameters. In this work, existing and potential risk-factors are investigated in a local cohort, with the ultimate aim of identifying new risk-factors for AVF failure, and opening new pathways for risk-factor identification in the future.
Three main avenues were followed: The first approach involved using health informatics, electronic records and data linkage to create an accurate picture of a patients AVF timeline. This retrospective single centre study assessed known risk-factors such as age and diabetes, and various serological markers such as albumin, c-reactive protein, ferritin and phosphate in 137 patients. AVF patency rates were also examined in this cohort. Decreased pre-operative levels of ferritin and increased phosphate were markers of interest due to association with AVF failure at 1-year. Known risk-factors such as gender and age showed no effect on AVF outcome in this cohort. Primary patency was observed to be 67% at one-year, in line with literature values, and primary assisted patency 91 %.
The second approach assessed if modern ultrasound markers of arterial elasticity (shear wave elastography) and strain (velocity vector imaging) were feasible methods of assessing arterial stiffness in the peripheral vasculature in a group of 40 volunteers and 47 patients. The methods were then assessed to determine if they could act as risk factors for AVF failure in 33 patients who underwent AVF creation. Both methods were feasible for the assessment of the peripheral vasculature, showing good repeatability, homogeneity, and were straight-forward to implement. Using shear wave elastography an increase in brachial artery elasticity following AVF creation was observed. None of the markers studied could be proven to act as risk-factors for AVF failure.
The third approach aimed to determine if 3T MRI sequences was a feasible modality for the pre-operative workup and followup of these patients in a prospective study of 6 patients and 10 healthy volunteers, using three different sequences. 3T MRI was found to agree with measurements from ultrasound, and also provided the benefit of 3D depiction of the vessels and high resolution. Finally, using these same MRI images, it was demonstrated that computational fluid dynamics simulations do not produce equal results if one changes the MRI sequence used for geometry acquisition.
The difficulty in identifying reliable risk-factors suggests that a multi-factorial approach may be beneficial. Studies with larger cohorts, and longer followup which combine serological markers, comorbidities, and results from imaging may be needed to identify risk-factors which finally increase patency rates.
|Date of Award||2019|
|Supervisor||Graeme Houston (Supervisor) & Rose Ross (Supervisor)|