Heart Valve Prosthesis Leaflet Curvature for Thromboresistance
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Solution Overview
Problem
Existing heart valve prostheses disrupt the homogeneous laminar structure of blood flow, leading to blood stagnation zones and potential thrombotic complications due to leaflet design features that increase the risk of thrombus formation and trauma to blood elements.
Innovation Solution
A heart valve prosthesis with an annular housing and leaflets that pivot around a reference axis, featuring radially oriented console projections and matching slots, spherical hinge surfaces, and conical downstream surfaces to minimize disturbances in blood flow and reduce the number of hinged joints, ensuring smooth blood passage and closure without stagnation zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If leaflets are designed with multiple projections and support surfaces to ensure proper closure and prevent backflow, then valve reliability is improved, but blood flow homogeneity deteriorates due to creation of stagnation zones
Solution Approach 1:
The leaflets are designed with a specific curvature where the upstream surface is convex and the downstream surface is concave, allowing smooth blood flow along the curved surfaces without creating stagnation zones. The coaptation surfaces are also curved to ensure proper sealing while maintaining flow homogeneity.
Solution Approach 2:
Different surfaces of the leaflets have different geometric properties optimized for specific functions: the upstream surface has convex curvature for smooth flow entry, the downstream surface has concave curvature for flow attachment, and the coaptation surfaces have specific curvature for proper sealing. This local differentiation allows simultaneous achievement of reliable closure and flow homogeneity.
2Object-generated harmful factors
If leaflet pivoting limiters are provided at the end surface of the housing to increase flow homogeneity, then blood flow structure is improved, but prosthesis dimensions increase and leaflet mobility may be restricted
Solution Approach 1:
The pivoting limiter function is merged with the coaptation surfaces of the leaflets themselves. The limiters are not separate components at the housing end surface but are integrated into the leaflet structure, eliminating the need for additional housing extensions while maintaining flow homogeneity.
Solution Approach 2:
Instead of providing limiters at the housing end surface that extend outward, the limiting surfaces are positioned on the leaflets themselves, inverting the conventional approach. This allows the leaflets to self-limit their pivoting angle while maintaining a compact prosthesis overall dimension.
3Object-generated harmful factors
If console projections and slots are provided to reduce the number of hinged joints and minimize blood flow disturbances, then thromboresistance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The hinge joint surfaces are designed as spherical segments rather than flat surfaces. The console projections have spherical convex surfaces that mate with spherical concave surfaces in the slots. This spherical geometry provides self-aligning properties that reduce sensitivity to manufacturing tolerances while minimizing blood flow disturbances.
Solution Approach 2:
The hinge joint design transitions from conventional flat-to-flat contact to spherical-to-spherical contact, changing the geometric parameters. This parameter change increases the contact area and provides rotational freedom, reducing the impact of manufacturing precision variations on joint performance.
Data Source
AI summary
A medical device in cardiac surgery for replacement of the diseased native heart valves in humans increases thromboresistance of heart valve prosthesis. A heart valve prosthesis comprising an annular housing with the inner surface defining the blood flow I through the valve prosthesis and leaflets mounted within the annular housing with the possibility to pivot around the reference axis between an open position which allows the passage of the direct blood flow I, and a closed position which restricts the blood backflow II. Each leaflet has an upstream surface facing the direct blood surface I, a downstream surface facing the blood backflow II, a coaptation surface, and a side surface.