AV Flow Restrictor Stent With Central Stenosis for Dialysis Patency
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Solution Overview
Problem
Current dialysis access methods, such as AVFs and AVGs, suffer from poor long-term patency and accessibility due to abnormal flow dynamics, leading to frequent graft or fistula failure and the need for frequent access point creation, which is costly and burdensome for healthcare.
Innovation Solution
A deployable stent flow restrictor combining self-expanding and balloon expandable stents is implanted via a catheter, creating a narrowed central section to regulate flow and pressure within dialysis grafts or fistulas, using self-expansion or balloon expansion to achieve a desired narrowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dialysis graft or fistula is created to provide large volume blood access, then dialysis access capability is improved, but long-term patency deteriorates due to abnormal flow dynamics and body's physiologic defenses
Solution Approach 1:
The stent incorporates a narrowed central section with different dimensional properties than the end sections. This localized geometric variation creates a flow restrictor effect in the central portion while maintaining adequate lumen diameter at the ends for cannulation, thereby improving flow dynamics locally without compromising overall access capability
Solution Approach 2:
The stent geometry is designed with specific dimensional parameters where the central section has a reduced diameter compared to the end sections. This parameter change creates controlled stenosis that modifies flow velocity and pressure distribution, reducing abnormal high-flow states that trigger physiologic defenses and thrombosis
2Reliability
If the graft lumen is narrowed to improve flow dynamics, then pressure and pulsation are reduced improving hemodynamic properties, but access difficulty increases due to smaller target size
Solution Approach 1:
The stent creates localized narrowing only in the central section while maintaining larger diameter at the proximal and distal ends. This allows the flow-restricting function to be concentrated where needed for hemodynamic improvement while preserving adequate access targets at the ends for needle cannulation by trained technologists
Solution Approach 2:
The stent is divided into functional segments: end sections with larger diameter for access and a central section with narrowed diameter for flow regulation. This segmentation allows each portion to fulfill its specific function - the ends provide access targets while the central portion provides hemodynamic control
3Reliability
If a stent is implanted to create a narrowed central section, then flow restriction and patency are improved, but device complexity increases due to deployable structure requirements
Solution Approach 1:
The stent is designed as a deployable structure that transitions from a compressed delivery state to an expanded deployed state. This dynamic configuration allows the complex geometric shape with narrowed central section to be delivered through standard catheters and then self-expanded or balloon-expanded to the final functional configuration, managing structural complexity through state transformation
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
Improves long-term patency and reduces thrombosis risk by stabilizing flow dynamics, extending the lifespan of dialysis access and reducing the frequency of access point creation.
Implementation Method 1
the stent is self-expanding when released from a sheath
Implementation Method 2
or expanded with a balloon
Data Source
AI summary
A stent is provided with a central portion between two end portions, and with the central portion narrower than the end portions to provide a stenosis within the stent, such as for improving function of a dialysis graft or fistula. The stent can be merely a metal wire cage or can additionally include a liner inside and/or outside of the metal cage. One stent includes tapering transitions between the end portions and the central portion. The stent can be self-expanding with a retracted form held by a surrounding sheath until the sheath is retracted and the stent returns to its biased expanded form. A balloon can provide a radial expansion force to expand the stent. The balloon or self-expansion can expand the stent partially, with the central portion narrower than the end portions, and optionally further expanded to have a diameter matching that of the end portions.