Stent Delivery Apparatus with Rip Cord Trigger Wires

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Solution Overview

Problem

The deployment of stents in vascular systems often results in inaccurate placement and potential damage due to rapid and irregular expansion of stent struts, along with longitudinal movement during sheath withdrawal, which can lead to vessel damage and reduced accuracy.

Innovation Solution

A stent delivery apparatus with a restraining device, such as a rip cord, and trigger wires that securely hold the stent in a radially inward compressed configuration, allowing controlled release and expansion, minimizing deployment forces and preventing unwanted longitudinal movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the sheath is withdrawn from the stent, then the stent expands radially outward, but the stent moves longitudinally out of position and expands in an uncontrolled manner

Engineering Contradiction:

Improvestent placement accuracyVSAvoidstent expansion control

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The stent is pre-loaded onto the delivery catheter in a compressed state, and the delivery system is navigated to the target site before deployment. The sheath is positioned over the stent during delivery, and only after precise positioning is achieved does the sheath withdrawal initiate controlled expansion. This preliminary positioning action ensures the stent is at the correct location before expansion begins.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The delivery sheath acts as an intermediary mechanism that provides controlled radial compression to the stent during delivery and positioning. By gradually withdrawing the sheath, the compression force is gradually released, enabling controlled radial expansion. The sheath mediates between the compressed stent state and the expanded deployed state, preventing uncontrolled expansion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If trigger wires are used to control stent release, then the stent can be held in compressed configuration during delivery, but the trigger wire system becomes complicated

Engineering Contradiction:

Improvestent release controlVSAvoidtrigger wire system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention extracts the release control function from the complex trigger wire system and integrates it directly into the delivery catheter structure. The delivery catheter itself provides the restraining force through its interaction with the stent, eliminating the need for separate trigger wires. This simplifies the overall system while maintaining precise release control.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The delivery catheter and release control mechanisms are merged into a single integrated system. The catheter structure itself serves both as the delivery vehicle and as the release control mechanism, combining multiple functions into one component. This integration reduces the number of separate parts and simplifies the overall device architecture.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If the stent expands rapidly upon sheath removal, then the stent reaches its expanded configuration quickly, but the rapid expansion may deform or damage stent struts and the vessel

Engineering Contradiction:

Improvedeployment speedVSAvoidvessel damage and stent deformation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The sheath withdrawal is performed in a controlled, gradual manner rather than as a single rapid action. The sheath is withdrawn incrementally, allowing the stent to expand in a staged fashion. This periodic or stepwise release of compression force enables the stent to expand at a controlled rate, preventing the harmful effects of rapid expansion while still achieving deployment efficiently.

Inventive Principle:

Principle #19Periodic action

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

Enables precise and controlled deployment of stents with reduced risk of damage to the vessel, ensuring accurate positioning and minimizing the force required for deployment, thereby improving the accuracy and safety of stent placement.

Implementation Method 1

a stent made of a shape-memory alloy such as Nitinol may allow the stent to return to a predetermined expanded configuration upon removal of a sheath or other device that maintains the stent in its compressed, pre-deployment configuration

Methodology Applied

Scientific EffectShape memory alloy: Shape Memory Alloy

Implementation Method 2

A restraining device exerts a force on the stent in a radially inward direction for releasably restraining the proximal stent end in a radially inward compressed condition

Methodology Applied

Scientific EffectMechanical force: Mechanical Force

Data Source

PatentEP2745810B1Apparatus for deployment of a stent

Publication Date: 2020.10.14 COOK MEDICAL TECHNOLOGIES LLC

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AI summary

In an apparatus for deployment of an implantable medical device including a stent graft, a restraining device (54), such as cord or suture, holds at least the proximal end (30) of the stent in a radially inwardly compressed configuration during delivery to a desired location within the lumen of a patient's vessel. Withdrawal of one or more trigger wires (58, 60) facilitates the release and removal of the restraining cord from the proximal end of the stent so as to allow the stent to become fully deployed within the vessel.