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Hemodynamic impact of anastomosis size and angle in side-to-end arteriovenous fistulae: a computer analysis
Koen Van Canneyt1, Thierry Pourchez, Sunny Eloot
1Institute of Biomedical Technology (IBiTech), Ghent University, Ghent, Belgium. Koen.VanCanneyt@UGent.be
Insights
This study reveals that arteriovenous fistula (AVF) anastomosis size and angle significantly impact hemodynamics. Larger openings and wider angles improve flow, while sharp angles can reverse arterial flow, crucial for hemodialysis access.
Area of Science:
- Biomedical Engineering
- Cardiovascular Physiology
- Medical Device Design
Background:
- Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis.
- AVF complications often overlook the anastomosis (connection segment).
- Hemodynamic factors influencing AVF function require further investigation.
Purpose of the Study:
- To mathematically investigate the hemodynamic impact of anastomosis size and angle on pressure drop and flow distribution in AVFs.
- To analyze how variations in anastomosis geometry affect blood flow dynamics within the access.
Main Methods:
- A computational model of a side-to-end AVF was developed.
- Substudies focused on varying anastomosis cross-sectional area and angle.
- Pressure drop and flow distribution were calculated across a range of arterial inflow rates (600-1200 mL/min).
Main Results:
- Increased anastomosis area and angles wider than 43 degrees reduced pressure drop.
- Larger anastomosis areas shifted flow predominantly to the proximal vein.
- Anastomosis angles exceeding 58 degrees led to insufficient flow and potential distal arterial flow reversal.
Conclusions:
- Anastomosis size and angle are critical, underestimated factors influencing AVF hemodynamics.
- These geometric parameters significantly affect pressure drop and flow distribution in AVFs.
- Optimizing anastomosis geometry could improve AVF function and reduce complications.
Purpose:
An arteriovenous fistula (AVF) is the first choice vascular access for hemodialysis. The AVF pathway can be seen as consisting of seven segments: proximal artery, distal artery, arterial collaterals, proximal vein, distal vein, venous collaterals, and the anastomosis. While most studies describe access complications without considering the impact of the anastomosis (7th segment), the present mathematical study investigated the hemodynamic impact of anastomosis size and angle on pressure drop and flow distribution.
Methods:
A side-to-end AVF model was developed, consisting of an anastomosis with a given cross-sectional area (substudy 1) and angle (substudy 2). Starting from two reference cases (one for each substudy) with fixed flow distribution, pressure drop over the anastomosis was calculated for an arterial inflow in the range 600 to 1200 mL/min. The same reference cases, subsequently with fixed pressure boundary conditions, were further used to assess flow distribution over the proximal vein and distal artery.
Results:
Pressure drop decreased with a larger anastomosis cross-sectional area and an angle wider than 43 degrees , while it was almost stable for smaller angles. Although proximal arterial inflow increased for larger anastomosis areas, the overall flow distribution shifted almost totally to the proximal vein. When the anastomosis angle exceeded 58 degrees , the proximal arterial inflow was not sufficient to deliver enough flow, leading to distal arterial flow reversal.
Conclusion:
Despite the underestimation of the hemodynamic impact of the anastomosis size and angle in the literature, this study showed major influences on the pressure drop over the anastomosis and, with it, on flow distribution towards the arterial and venous outflow.
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