Coronary Stent with Smooth Expanded Surface
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Solution Overview
Problem
Existing stents expand to form a twisted lattice configuration, leading to local blood-flow turbulences due to uneven outer surfaces, which can have adverse effects on blood cells.
Innovation Solution
A method of fabricating a stent with a lattice configuration that maintains a smooth outer surface in its expanded state by forming links and openings in a tubular body with a dimension equal to the fully expanded state, allowing for contraction to a smaller diameter for delivery and subsequent expansion to the original diameter, either by using a flexible tube or a truss structure, ensuring all radial outer surfaces lie in a continuous cylindrical surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a stent is expanded to form a lattice configuration with individual links separated by enlarged openings, then the stent can be delivered through the vascular lumen and deployed at the desired site, but the outer surfaces of the individual links become uneven and twisted, creating local blood-flow turbulences
Solution Approach 1:
The stent is pre-formed with a smooth outer surface at its fully expanded diameter before contraction. Geometric patterns are removed through the wall to form a lattice configuration that maintains the smooth outer surface. This preliminary preparation ensures that when the stent is later expanded at the deployment site, it achieves a smooth outer surface configuration that minimizes blood-flow turbulence.
Solution Approach 2:
The stent utilizes changes in dimensional parameters between contracted and expanded states. In the contracted state, the stent has a reduced diameter for deliverability. Upon expansion, it returns to its original diameter where the lattice configuration maintains a smooth outer surface. This parameter change allows the stent to transition from a deliverable state to a deployed state with optimized hemodynamic characteristics.
2Object-affected harmful factors
If the stent is formed with a smooth outer surface in its expanded configuration, then blood-flow turbulence is minimized, but the manufacturing process becomes more complex
Solution Approach 1:
The smooth outer surface and lattice configuration are created in advance during the initial formation of the stent at its fully expanded diameter. By performing the geometric pattern removal and lattice formation before contraction, the manufacturing process simplifies the subsequent deployment steps while ensuring the desired smooth outer surface is achieved.
Solution Approach 2:
Instead of forming the lattice configuration first and then attempting to smooth the outer surface after expansion, the invention inverts the approach by first creating the lattice in a tube with the final expanded diameter, ensuring the smooth outer surface is inherent to the structure from the beginning.
3Length of moving object
If the stent is contracted to a smaller dimension for delivery, then it can be passed through the vascular lumen, but the individual links become distorted and twisted
Solution Approach 1:
The stent is designed to be dynamic in its configuration, transitioning between contracted and expanded states. The lattice structure allows the individual links to distort and twist during contraction for deliverability, while returning to their original smooth configuration upon expansion. This dynamic behavior enables the stent to adapt its shape according to the delivery and deployment requirements.
Solution Approach 2:
The stent utilizes parameter changes in its dimensional state to manage link configuration. In the contracted state, the reduced diameter allows for easier delivery despite link distortion. Upon expansion to the original diameter, the links return to their intended configuration with smooth outer surfaces, optimizing both deliverability and hemodynamic performance.
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 reduces the likelihood of turbulence in blood flow and simplifies the manufacturing process, providing a stent with a smooth outer surface in its in-use configuration that matches the diameter of the blood vessel, thereby minimizing adverse effects on blood cells and enhancing ease of manufacture.
Implementation Method 1
The contracting step may include placing the stent in a flexible tube and reducing the dimension of the flexible tube in order to contract the stent therein.
Implementation Method 2
The contracting step may include placing the stent in a truss structure that when axially stretched, shrinks the stent in an axisymmetric, uniform fashion to its contracted configuration.
Data Source
AI summary
A coronary stent is disclosed herein as having a lattice configuration on a generally thin-walled cylindrical tube. This particular stent is fabricated using an elongated thin-walled tubular solid that has a diameter equal to that of the final expanded configuration of the stent. In other words, the lattice configuration is cut onto the surface of the tubular solid that has a diameter substantially equal to the inner diameter of the blood vessel for which the stent is intended. The tubular lattice is then shrunk (collapsed) axisymmetrically to a new cylindrical configuration with a diameter substantially less than the blood vessel for which the stent is intended. The stent in its reduced diameter state can then be delivered to a desired site in the body via a catheter with an inflatable balloon at its distal portion. Upon the inflation of the balloon, the stent will assume its expanded, deployed configuration into the original diameter at the desired site in the body.