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Hemodialysis vascular dysfunction

Hemodialysis vascular access dysfunction is one of the major causes of morbidity and hospitalization among the population undergoing hemodialysis procedure. Vascular access has three major types that include PTFE grafts, arteriovenous fistula (AVF), and catheters among which the AVF is the most preferred form due to its lower infection rate, lower risk of thrombosis, and higher patency rate. These advantages have made the AVF the first choice of the vascular access. However, failure of AVF to mature and formation of thrombosis in matured fistulas have been the major causes of morbidity and mortality in hemodialysis patients. Progression of stenosis, which occurs due to adverse remodeling in AVFs, is one of the major underlying factors under both scenarios. Early diagnosis of adverse modeling of the stenosis in an AVF can provide an opportunity to intervene in a timely manner for either assisting the maturation process or avoiding the thrombosis.

We, at the “TEM Laboratory”, UC, conduct research on functional diagnostic parameters that can better predict the status of AVF functionality. These diagnostic parameters are developed based on fluid mechanics fundamental, which are based on the pressure drop-flow relationships in stenosed vessels. In order to achieve our goal, we have performed in vivo experiments (pig models), image processing techniques and computational fluid dynamics (CFD) over a one month period. We use CFD to obtain the flow field in the 3 dimensional models of AVF reconstructed from the CT scans or other imaging techniques. This enables us to identify the possible regions of vascular stenosis in the AVF. Subsequently, we correlate the severity of stenosis with our new diagnostic endpoints, namely as pressure drop coefficient (Cp) and resistant index (R). The figures below show the distribution of pressure drop for two AVFs with favorable (FR) and adverse remodeling (AR) at 2 days (2D), 7D, and 28D post-surgery. The AVF with FR went through larger luminal dilation, had higher flow rate, lower pressure drop, and lower % area stenosis as compared to the AVF with AR. It is noteworthy that, the AVF with AR formed a severe stenosis after 28D post-surgery, while the AVF with FR remained patent. Also it can be noted that the AVF with FR had lower values of Cp and R as compared to the AVF with AR, which formed a stenosis at 28D.

fistula-figure 1 

 

fistula-fig 2 

by zopeown last modified 2015-05-06 11:14