Transcatheter Valve Delivery Tethers for Controlled Stent Expansion
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Solution Overview
Problem
Current transcatheter prosthetic heart valve delivery systems face challenges with uncontrolled rapid expansion of the stent frame during deployment, leading to potential misplacement of the valve, as the stent sections expand at different rates, causing the valve to thrust past the intended anatomical location.
Innovation Solution
A delivery device with an outer sheath assembly, inner shaft assembly, and tethers that constrain and control the expansion of the stent frame, allowing for controlled deployment by maintaining tension on the tethers to prevent rapid expansion, and enabling recapture of the stent frame for precise placement and repositioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the stent frame is designed to self-expand rapidly upon deployment, then the valve can be delivered through a compressed catheter, but the rapid expansion causes uncontrolled thrusting past the intended anatomical location
Solution Approach 1:
The stent frame is divided into multiple independently controllable sections (first stent section, second stent section, third stent section) that can be deployed sequentially rather than simultaneously. This segmentation allows each section to expand at a controlled rate, preventing the uncontrolled rapid thrusting that occurs with simultaneous expansion of the entire frame.
Solution Approach 2:
The delivery system incorporates dynamic control mechanisms including tethers that can be selectively released and a handle assembly that controls the expansion timing of each stent section. This dynamic control allows the system to transition from a static compressed state to a controlled sequential expansion process, enabling precise deployment at the intended anatomical location.
2Shape
If different stent sections expand at different rates, then complex valve shapes can be achieved, but the valve springs off the retainer in an uncontrolled fashion
Solution Approach 1:
The system incorporates feedback control through the tether mechanism that monitors and responds to the expansion state of each stent section. As each section expands, the tether provides feedback to the handle assembly, allowing real-time adjustment of the expansion process to maintain control and prevent uncontrolled spring-off of the valve.
Solution Approach 2:
The tethers are pre-configured to be released in a specific sequence before full expansion occurs. This preliminary action of releasing tethers at controlled intervals prevents the valve from springing off the retainer in an uncontrolled fashion while still allowing different stent sections to expand at different rates to achieve the desired complex valve shape.
3Ease of operation
If the stent frame is crimped to a small diameter for delivery, then percutaneous transluminal delivery is enabled, but the inflow section may thrust into the left ventricle instead of engaging the annulus
Solution Approach 1:
The stent frame is segmented into multiple sections with the inflow section, outflow section, and intermediate sections that can be controlled independently. This segmentation allows the inflow section to be held in place during delivery while other sections expand, preventing the inflow section from thrusting into the left ventricle while still enabling percutaneous transluminal delivery through compression.
Solution Approach 2:
The system uses dynamic control mechanisms including the handle assembly and tether release system to control the expansion timing of each stent section. This dynamic control ensures that the inflow section remains compressed during delivery for easy percutaneous transluminal delivery, then expands in a controlled manner at the intended anatomical location to engage the annulus precisely.
4Productivity
If the sheath is retracted to allow expansion, then the valve can be deployed, but the stent frame cannot be recaptured for repositioning
Solution Approach 1:
The tethers are designed to be released in a controlled sequence during the deployment process, which allows the stent frame to be held in place during initial expansion for efficient deployment, but then enables recapture if needed. This preliminary controlled release of tethers provides adaptability for repositioning while maintaining deployment efficiency.
Solution Approach 2:
The delivery system incorporates dynamic control mechanisms that allow the sheath to be retracted in a controlled manner to enable deployment, while the tether system can be manipulated to maintain or restore capture capability. This dynamic control provides both rapid deployment and the versatility to recapture and reposition the stent frame if necessary.
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
Ensures controlled and precise deployment of the prosthetic heart valve, reducing the risk of misplacement and allowing for recapture and repositioning of the stent frame, facilitating safe and effective implantation at the intended anatomical site.
Implementation Method 1
maintaining tension on the tethers to prevent rapid expansion
Implementation Method 2
the stent frame is configured to self-expand from a compressed condition to a normal, expanded condition
Data Source
AI summary
A heart valve therapy system includes a delivery device and a stented valve. The delivery device includes an outer sheath, an inner shaft, an optional hub assembly, and a plurality of tethers. In a delivery state, a stent frame of the prosthesis is crimped over the inner shaft and maintained in a compressed condition by the outer sheath. The tethers are connected to the stent frame. In a partial deployment state, the outer sheath is at least partially withdrawn, allowing the stent frame to self-expand. Tension in the tethers prevents the stent frame from rapidly expanding and optionally allowing recapture. Upon completion of the stent frame expansion, the tethers are withdrawn.