Low-Profile Heart Valve Stent Layout for Accurate TAVR Deployment
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Solution Overview
Problem
Existing collapsible/expandable transcatheter aortic valve replacement (TAVR) devices face challenges with delivery system profile and deployment accuracy, particularly due to stent foreshortening during expansion, which affects alignment and positioning within the native valve annulus, leading to potential regurgitation and conduction disturbances.
Innovation Solution
A prosthetic heart valve with a stent structure featuring low cell density, strategic foreshortening, and directional expansion, utilizing cobalt chromium or stainless steel, which allows the inflow end to remain static while the outflow end moves axially during deployment, improving alignment and reducing the delivery profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stent is designed with vertical bars extending along most or the entire length of the stent, then the structural strength is improved, but the delivery profile becomes larger when collapsed
Solution Approach 1:
The stent is divided into different zones with different strut configurations. The first end (inflow end) has struts extending along most of the length for strength, while the second end (outflow end) has struts that do not extend along most of the length, reducing the collapsed profile. This segmentation allows different parts of the stent to have different characteristics optimized for their specific functions.
2Volume of moving object
If the stent undergoes foreshortening during expansion, then the delivery profile is reduced, but the deployment accuracy deteriorates due to alignment shifts
Solution Approach 1:
Different portions of the stent are designed with different foreshortening characteristics. The first end (inflow end) is designed to remain substantially static during expansion, while the second end (outflow end) is designed to move axially toward the first end. This local differentiation allows the stent to achieve both profile reduction and deployment accuracy.
Solution Approach 2:
Instead of having uniform foreshortening throughout the stent, the invention inverts the expected behavior by designing the first end to remain static while the second end moves during expansion. This inverted approach ensures that the reference point for alignment (first end) does not shift, thereby maintaining deployment accuracy while still achieving profile reduction through controlled foreshortening at the second end.
3Strength
If the stent is designed with high cell density, then the structural integrity is improved, but the delivery profile becomes larger
Solution Approach 1:
The stent is segmented into different zones with different cell densities. The first end (inflow end) has higher cell density for structural integrity, while the second end (outflow end) has lower cell density to reduce the collapsed profile. This allows the stent to maintain strength where needed while minimizing delivery profile.
Solution Approach 2:
Different portions of the stent have different cell densities optimized for their specific functions. The first end has higher cell density for structural support and stability during deployment, while the second end has lower cell density to reduce the overall collapsed profile and facilitate delivery through smaller vessels.
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 solution enhances deployment accuracy by maintaining the inflow end's position relative to the native valve annulus, minimizing alignment shifts, and allows for a smaller delivery profile, thereby reducing the risk of regurgitation and conduction disturbances.
Implementation Method 1
the stent may include a self-expanding or balloon-expandable stent, often made of nitinol or another shape-memory metal or metal alloy
Implementation Method 2
the stent is collapsible and expandable, extending in an axial direction from a first inflow end to a second outflow end
Data Source
AI summary
A prosthetic heart valve includes a radially collapsible and expandable stent, a cuff and leaflets sutured thereto. The heart valve extends axially between an inflow end and an outflow end and the stent includes a layout of struts and nodes having a hybrid combination of vertical struts and oblique struts in the form of diamond-shaped and half diamond-shaped cells. The layout of the structure is configured to preserve a low cell density of material used in the stent to reduce the stent profile while in a collapsed state and to improve the deployment accuracy of the stent into the native valve annulus.