Stent Graft Bridging Elements for Sealing and Flexibility

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Solution Overview

Problem

Zig-zag stent grafts with unsupported flaps of graft material at the proximal end can lead to incomplete sealing, blood leakage, migration, and premature wear due to blood flow and lack of support, while traditional bare stents cause erosion and reduce flexibility.

Innovation Solution

Incorporating bridging elements with greater flexibility than the stent struts, which extend between adjacent peaks to provide an expansion force and maintain graft material open, without compromising the device's compressibility and flexibility, and are designed to prevent direct contact with the vessel wall.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a zig-zag stent structure with greater openness is used to increase flexibility and compressibility, then the device can be compressed to a smaller diameter for introduction and remains more flexible in situ, but unsupported flaps of graft material are created between adjacent peaks that lead to incomplete sealing, blood leakage, and premature wear

Engineering Contradiction:

Improveflexibility and compressibilityVSAvoidsealing integrity and prevention of blood leakage

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The stent structure is segmented into multiple struts forming peaks and valleys, with bridging elements selectively placed between adjacent peaks at the proximal end. This segmentation allows the stent to maintain its zig-zag flexibility while adding localized support where needed to prevent graft material flaps and ensure sealing integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Bridging elements are applied locally between adjacent peaks at the proximal end of the stent, rather than uniformly across the entire stent structure. This local reinforcement provides necessary support to prevent unsupported flaps of graft material while preserving the overall flexibility and compressibility of the zig-zag stent design.

Inventive Principle:

Principle #3Local quality

2Reliability

If bare stents are used to support the proximal end of the graft member and urge it against vessel walls, then sealing and positioning are improved, but vessel wall erosion occurs and flexibility is reduced

Engineering Contradiction:

Improvesealing and positioningVSAvoidvessel wall erosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Bridging elements serve as intermediary structures between the stent peaks and the graft material, providing indirect support to urge the graft against the vessel wall. This intermediary approach achieves reliable sealing and positioning while avoiding direct contact between bare metal stents and the vessel wall, thereby preventing erosion.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If bridging elements with greater flexibility than stent struts are used to maintain graft material open, then proper seal and patency are ensured without compromising device compressibility, but the structural strength is reduced

Engineering Contradiction:

Improveseal and patencyVSAvoidstructural strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The bridging elements are designed with different flexibility parameters compared to the main stent struts. By adjusting the flexibility parameter of the bridging elements to be greater than that of the stent struts, the invention achieves proper seal and patency while maintaining device compressibility, as the more flexible bridging elements can deform more easily during compression and expansion cycles.

Inventive Principle:

Principle #35Parameter changes

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 bridging elements ensure a proper seal and patency of the stent graft against the vessel wall, preventing blood leakage and migration, while maintaining flexibility and compressibility, and protecting the vessel wall from trauma.

Implementation Method 1

the bridging elements produce in use an expansion force urging graft material of said graft element in a graft opening direction

Methodology Applied

Scientific EffectElastic expansion: Elasticity

Data Source

PatentUS10195015B2Implantable medical device

Publication Date: 2019.02.05 COOK MEDICAL TECHNOLOGIES LLC

AI summary

A stent graft includes a tubular graft element to which there are attached a plurality of stent rings. The stent rings are formed of a plurality of stent struts arranged in a zig-zag arrangement with alternating peaks and valleys. The end-most stent is located at the proximal end of the graft tube. Between adjacent peaks of the end most stent, there is provided a series of bridging elements. These are preferably formed of Nitinol wire and to be substantially more flexible than the stent struts. The bridging elements extend in the region of graft material between adjacent stent peaks and are attached to the graft material, for example by suturing. The bridging elements are substantially more flexible than the stent ring and therefore impart little opening force on the graft material in comparison to the force produced by the stent ring. However, the bridging elements impart enough force on the flaps of graft material between the peaks of the stent ring keep these flaps open, that is against the vessel wall. The bridging elements can provide integral barbs.