Fistula Flow-Directing Vanes for Helical Blood Flow
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Solution Overview
Problem
Arteriovenous fistulas have low success rates in maturation and are prone to neointimal hyperplasia, leading to stenosis and failure, due to turbulent flow and inadequate vessel dilation, which existing devices fail to adequately address.
Innovation Solution
A medical device with an annular body and flow-directing vanes is implanted within the fistula to induce circumferential velocity components in blood flow, promoting patency by creating a helical flow that enhances vessel remodeling and reduces tissue proliferation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional arteriovenous fistulas are created without flow-directing devices, then the structure is simple and easy to implement, but the fistula maturation success rate is low and neointimal hyperplasia occurs frequently
Solution Approach 1:
The flow director device is divided into multiple functional segments: an annular body for structural support, multiple flow-directing vanes for creating helical flow, and barbs for anchoring. This segmentation allows each component to perform its specific function optimally while maintaining overall device effectiveness in promoting fistula maturation and reducing neointimal hyperplasia
Solution Approach 2:
The flow director employs curved and helical geometric features, including helical vanes that wrap around the annular body in a spiral configuration. This curvature is specifically designed to generate helical flow patterns in blood, which has been shown to reduce neointimal hyperplasia and improve fistula patency while maintaining reasonable device complexity
2Productivity
If high flow rates are achieved through arteriovenous fistulas for dialysis, then dialysis treatment time is minimized, but turbulent flow causes neointimalhyperplasia and stenosis
Solution Approach 1:
The device converts the harmful turbulent flow into beneficial helical flow by using angled vanes that redirect blood flow in a spiral pattern. This helical flow maintains the high flow rates necessary for efficient dialysis while eliminating the turbulent characteristics that cause neointimalhyperplasia and stenosis, effectively transforming a harmful effect into a therapeutic benefit
Solution Approach 2:
The flow director utilizes hydraulic principles by designing vanes with specific angles and orientations that exploit blood flow dynamics to generate helical motion. The device passively redirects high-velocity blood flow into a controlled spiral pattern, using the kinetic energy of the blood itself to create the therapeutic flow pattern without requiring additional power sources
3Reliability
If vessels are allowed to dilate naturally without mechanical support, then the device structure remains simple, but inadequate vessel dilation occurs and fistula patency is compromised
Solution Approach 1:
The annular body is designed with non-uniform features including varied vane orientations, different vane angles, and asymmetric spacing between vanes. This local variation in structural properties allows different regions of the device to address specific local requirements for vessel dilation and flow direction, improving overall fistula patency while avoiding the need for a uniformly complex structure throughout
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device significantly improves fistula patency rates by promoting long-term functionality and reducing the likelihood of neointimal hyperplasia, with helical flow persisting downstream of the device, thus supporting effective hemodialysis and broader vascular applications.
Implementation Method 1
induce circumferential velocity components in the blood via the impingement so as to promote patency of the fistula
Implementation Method 2
Abnormal flow through an arteriovenous fistula is often observed with auscultation in the nature of characteristic vibration, believed likely to stem from turbulent flow through the vasculature
Data Source
AI summary
A device for promoting patency of a fistula includes an annular body and a plurality of vanes formed integrally with the annular body, and projecting inwardly from an inner radial surface thereof. The vanes are oriented so as to impart circumferential velocity components to blood passed through a lumen of the device, and such that an unobstructed line of sight parallel to a central axis of the annular body extends between adjacent ones of the vanes.