Extravascular AVF Device Barb Capture Hemodynamic Control
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Solution Overview
Problem
The surgical creation and maintenance of arteriovenous fistulas (AVFs) for hemodialysis are hindered by high failure rates due to stenosis and thrombosis, primarily caused by neointimal hyperplasia and abnormal hemodynamic conditions, resulting in suboptimal patency rates and frequent secondary interventions.
Innovation Solution
A device comprising two device halves with anastomosis windows and barb ridges is used to facilitate side-to-side AVF creation, minimizing direct contact between intimal surfaces and providing a defined geometry for blood flow, which helps in maintaining patency by stabilizing the vascular connection through barb capture spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surgical creation of AVF is performed to increase blood flow rate, then hemodialysis treatment time is minimized, but failure rate increases due to stenosis and thrombosis
Solution Approach 1:
The device serves as an intermediary structure between the artery and vein, providing a controlled interface that mediates the hemodynamic interaction. The device includes an arterial portion, a venous portion, and a connection portion that together create a controlled transition zone, reducing abrupt hemodynamic changes that cause neointimal hyperplasia and thrombosis
Solution Approach 2:
The device modifies hemodynamic parameters by providing a gradual transition in vessel diameter and flow characteristics. The connection portion with its specific geometry (length, width, curvature) changes flow velocity and pressure gradients, reducing turbulent flow and stagnation zones that lead to thrombosis, while maintaining adequate blood flow rates for hemodialysis
2Productivity
If large flow rates are achieved through AVF creation, then treatment efficiency is improved, but extreme dilation occurs resulting in oversized fistulas that fail
Solution Approach 1:
The device controls the geometric parameters of the fistula through its structured design. The connection portion has a defined length (e.g., 10-50mm), width, and curvature radius that prevent excessive dilation. The device maintains optimal vessel diameter ratios (e.g., arterial to venous diameter ratio of 0.5-2.0) to control flow dynamics and prevent oversizing
Solution Approach 2:
The connection portion incorporates controlled curvature with a specific radius (e.g., 5-20mm) to promote laminar flow and reduce flow separation. The curved geometry distributes shear stress more evenly along the vessel wall, preventing localized dilation and maintaining appropriate fistula dimensions
3Productivity
If venous tissue is exposed to abnormal hemodynamic conditions, then blood flow rate is increased, but neintimalhyperplasia occurs causing stenosis
Solution Approach 1:
The device gradually transitions hemodynamic parameters from arterial to venous conditions. The connection portion creates a progressive change in flow velocity (from high arterial velocity to lower venous velocity) and pressure, reducing the abrupt shear stress changes that trigger neointimalhyperplasia. The geometry is designed to maintain shear stress within physiological ranges throughout the transition zone
Solution Approach 2:
The connection portion acts as an intermediary transition zone that buffers the venous tissue from direct exposure to extreme arterial hemodynamic conditions. This intermediate structure allows gradual adaptation of the venous wall to increased flow, reducing the mechanical stimuli that cause pathological neointimalhyperplasia and subsequent stenosis
Data Source
AI summary
An extravascular anastomosis device for facilitating side-to-side arteriovenous fistula creation and maintenance of patency thereof is presented. The device comprises two device halves each containing an anastomosis window which is in fluid connection with an interior space of the device. Further, the device comprises a pair of vessel capture spaces in which portions of the vessels to be joined are captured. The invention also has an embodiment wherein a method of joining a vein and an artery in order to create a fistula is presented.