Evaluation of Clinical Effects of Angioplasty in Dialysis Arteriovenous Fistula using a Diagnostic Ultrasound System
Vascular access (VA) is an essential component of ensuring a patient is able to undergo safe and effective hemodialysis. Yet, creation and maintenance of VA requires significant clinical and financial resources. Currently, the autogenous arteriovenous (AV) fistula is the preferred access. Compared to other forms of VA such as grafts and catheters, AV fistulas have relatively low complication rates, long periods of viability, and can be cannulated numerous times which is necessary for patients undergoing long-term treatments. Despite these advantages, AV fistulas require continuous surveillance and intervention, to ensure they are can support successful hemodialysis. In practice, these secondary complications immensely add to a patient’s and clinician’s burdens that they all but eliminate their advantages over alternatives. We aim to develop a model that would use the physical and physiological parameters of a patient to optimally guide fistula creation to minimize these secondary burdens.
Certain areas of AV fistulas are known to preferentially develop stenotic segments, and are thus responsible for much of the limitations of successful use. This is because vascular remodeling and dilation are controlled by mechanical forces along the vessel, such as the wall shear rate (WSR) and the compliance of the vessel itself. There are regions wherein these forces combine to be far above or below physiological acceptable norms. However, due to the current dearth of measuring capabilities, these parameters have largely been ignored. Therefore, clinicians are left only to intervene once a stenotic region has developed, usually in the form of percutaneous angioplasty (PTA), to ensure that the AV fistula remains viable.
Currently, no clinically applicable diagnostic system exists to directly determine fistula mechanics; that is, there are no means to assess interactions of vessel elasticity and WSR at the bedside which are the very root of stenotic developments. We propose to build on our established research base in high spatial- and temporal-resolution ultrasound speckle tracking to create a vascular ultrasound elastography and shear rate imaging measurement tool. In this way we can measure differences in compliant and stenotic tissue elasticity and WSR to evaluate and guide interventional angioplasty effectiveness. We intend to do this through the following two aims.
Aim 1. Measure blood wall-shear rate and compliance of the AV fistula circuit before and after PTA. We hypothesize that treating stenoses locally will affect compliance and WSR in key areas that influence vascular remodeling. We will conduct a clinical observational study to determine how PTA within a stenotic area impacts the blood wall-shear rate and compliance of the access circuit (i.e. the feeding artery, peri-anastomotic region, and the vein).
Aim 2. Measure stenotic lesion compliance and wall shear before and after angioplasty. We hypothesize that angioplasty changes not only the diameter of the vessel, but also the compliance and WSR at the lesion site, influencing further vascular remodeling. We will measure wall-shear rate and compliance in stenotic regions undergoing angioplasty pre- and post-PTA to determine how it impacts the shear rate and the compliance of the lesion site.