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Computational analyses and design improvements of graft-to-vein anastomoses
P W Longest1, C Kleinstreuer, P J Andreotti
1Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh 27695-7910, USA.
Insights
Arteriovenous grafts used in hemodialysis often fail due to blockages. This study optimizes graft designs to reduce turbulent blood flow, aiming to improve graft longevity and patient outcomes.
Area of Science:
- Biomedical Engineering
- Cardiovascular Research
- Medical Device Design
Background:
- Arteriovenous grafts (AVGs) are crucial for hemodialysis access.
- A significant percentage of AVGs fail within the first year due to occlusive lesions at the venous anastomosis.
- Hemodynamic factors like wall shear stress and pressure gradients are implicated in vascular disease development.
Purpose of the Study:
- To geometrically design arteriovenous graft-to-vein configurations to minimize stenotic development.
- To compare the hemodynamic performance of different graft anastomotic designs.
- To provide quantitative recommendations for improved arteriovenous loop graft designs.
Main Methods:
- Numerical simulation of transient laminar 3-D hemodynamics.
- Utilized a novel blood rheological model.
- Compared three anastomotic configurations: a base case, the Bard-IMPRA Venaflo graft, and a new end-to-end design.
Main Results:
- Identified specific geometric designs that significantly reduce locally disturbed blood flow.
- Quantified the impact of different configurations on hemodynamic parameters.
- Established a design criterion based on reducing factors contributing to stenosis onset and progression.
Conclusions:
- Optimized graft geometry can significantly reduce adverse hemodynamic conditions at the anastomosis.
- The study provides data-driven recommendations for enhancing arteriovenous loop graft patency rates.
- The proposed improved graft design warrants further clinical investigation.
Abstract:
For hemodialysis patients, arteriovenous grafts are omnipresent. Unfortunately, a large percentage of such grafts fail within the first year after surgery because of occlusive lesions mainly at the venous anastomotic site. It is textbook knowledge that critical values of certain hemodynamic parameters, such as low (oscillatory) wall shear stresses, large sustained wall shear stress gradients, significant changes in wall shear stress angles, excessive radial pressure gradients, etc., play significant roles in the onset and/or development of vascular diseases. The idea is to geometrically design graft-to-vein configurations such that aggravating flow patterns are reduced, and hence stenotic developments are minimized. Focusing on a new blood rheological model in conjunction with three graft-to-vein anastomotic configurations, that is, a base case, the Bard-IMPRA Venaflo graft, and a new graft-end design, the corresponding transient laminar 3-D hemodynamics are numerically simulated and compared. The design criterion for the best performance of these junction geometries is the most significant reduction in locally disturbed flow as expressed by equally weighted indicator functions for the onset and progression of stenotic developments. As a result of this comparison study, quantitative recommendations for arteriovenous loop graft designs toward increased patency rates are provided. The resulting improved graft design will be scrutinized in clinical trials.