Actively Controllable Stent for Dynamic Sizing and Repositioning
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Solution Overview
Problem
Current endovascular graft devices face challenges such as limited repositionability, migration issues, and inadequate sealing due to fixed expanded diameters, which complicate the treatment of aneurysms and require pre-sizing that often results in mis-sized grafts and unstable seals, leading to increased morbidity and the need for emergency surgery.
Innovation Solution
A delivery system with a self-expanding/forcibly expanding stent lattice and motors that allow for precise expansion and repositioning within the body, using a memory to store expansion force curves and a mechanism to compare applied forces with predetermined curves for accurate positioning and sealing, along with retractable retention tines and controllably releasable disconnect mechanisms for post-deployment adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If pre-sizing is performed based on CAT-scan measurements, then the graft size can be determined before implantation, but this leads to mis-sized grafts and unstable seals
Solution Approach 1:
The stent lattice is designed to be actively controllable, allowing dynamic adjustment of the expanded diameter after implantation. The delivery system includes motors that can expand or contract the stent lattice to match the actual anatomical dimensions, transforming a static pre-sized device into a dynamically adjustable one that adapts to the true vessel size, thereby eliminating sizing errors from pre-sizing
Solution Approach 2:
The delivery system incorporates force sensors and memory units that store predetermined characteristic curves of the stent lattice expansion. During implantation, the system measures the actual force required to expand the stent and compares it with the stored curves to detect contact with the native annulus and determine optimal expansion diameter. This feedback mechanism replaces error-prone pre-sizing with real-time measurement and adjustment
2Ease of operation
If the stent lattice is forcibly expanded to a fixed diameter, then the implant can be deployed, but repositioning becomes impossible and migration occurs
Solution Approach 1:
The stent lattice is designed with active controllability, allowing it to be expanded, contracted, and repositioned after initial deployment. The delivery system maintains connection to the stent lattice through the delivery catheter, enabling the operator to adjust the implant position and expansion diameter even after deployment, thus preventing migration while maintaining deployment simplicity
Solution Approach 2:
The system allows changing the expansion diameter parameter of the stent lattice after deployment. By adjusting the expansion diameter to match the actual anatomical dimensions rather than relying on fixed pre-sizing, the implant achieves stable sealing without compromising the ability to reposition if needed
3Reliability
If barbs or hooks are incorporated to retain the endograft, then migration is reduced, but the device complexity increases and sealing remains compromised
Solution Approach 1:
The patent replaces the mechanical retention system (barbs and hooks) with an actively controllable expansion system. Instead of relying on mechanical interlocking features that increase structural complexity, the system uses controlled expansion forces and real-time adjustment capabilities to achieve both retention and sealing, eliminating the need for complex retention structures
4Ease of manufacture
If the final expanded diameter is fixed, then the device can be manufactured, but pre-sizing becomes critical and difficult leading to mis-sized grafts
Solution Approach 1:
The stent lattice is designed with active controllability, allowing the final expanded diameter to be adjusted after implantation rather than being fixed at manufacturing. The delivery system includes motors that can expand or contract the stent lattice to match the actual anatomical dimensions, transforming a static manufactured device into a dynamically adjustable one that eliminates pre-sizing errors
Solution Approach 2:
The system enables post-implantation changes in the expansion diameter parameter. Rather than requiring precise pre-determination of the final diameter during manufacturing and pre-sizing, the actual expansion diameter is determined in-situ through force measurement and adjustment, allowing standard manufacturing processes while achieving precise sizing
Data Source
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AI summary
A method for implanting a stent includes contracting a self-expanding/forcibly-expanding stent of a shape-memory material set to a given shape to a reduced implantation size with a delivery system having drive wires. The stent has a selectively adjustable assembly with adjustable elements operatively connected to the drive wires such that, when the adjustable elements are adjusted by the drive wires, a configuration change in at least a portion of the self-expanding stent occurs. The contracted stent is inserted into a native annulus in which the stent is to be implanted. The drive wires are rotated with the delivery system to forcibly expand the stent into the native annulus. While rotating the drive wires, a torque applied to the drive wires is determined with the delivery system. Rotation of the drive wires is stopped based upon a value of the determined torque.