Self-Expanding Nitinol Stent for Pediatric Aortic Coarctation
Solution Overview
Problem
Current treatments for aortic coarctation, such as surgery, angioplasty, and stenting, face challenges including complications like reoccurrence, aneurysm formation, and the lack of suitable stents for pediatric patients, particularly those weighing less than 10 kg, due to growth-related issues and migration of implanted stents.
Innovation Solution
A radially self-expanding stent with a plurality of struts and joints that produce an outward radial force, capable of expanding from a compact diameter to a fully expanded diameter, designed to resist elastic recoil and accommodate vessel growth, made from materials like Nitinol for shape-memory properties, allowing for deployment in small patients and continued expansion with patient growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a stent is designed with sufficient radial force to resist elastic recoil in small vessels, then the stent can effectively treat aortic coarctation in pediatric patients, but the stent may cause damage to the vessel wall due to excessive force
Solution Approach 1:
The stent utilizes shape memory alloy material properties that allow it to change its radial force output based on temperature and mechanical deformation parameters. The stent is delivered in a compressed state at body temperature, then heated (e.g., with warm saline) to trigger phase transformation and generate controlled radial expansion force, ensuring the force remains within safe limits for pediatric vessel walls throughout the expansion process
Solution Approach 2:
The stent employs a dynamic expansion mechanism where the radial force is not applied instantaneously but progressively through controlled phase transformation of the shape memory alloy. The stent structure includes adjustable struts and joints that allow gradual expansion from compact to fully expanded diameter, enabling the radial force to be tuned and controlled to match the specific needs of different vessel sizes and prevent wall damage
2Volume of moving object
If a stent is made small enough to be delivered in pediatric patients, then the stent can be implanted in patients weighing less than 10 kg, but the stent lacks sufficient radial force to resist elastic recoil in small vessels
Solution Approach 1:
The stent is delivered in a compressed state with reduced dimensions suitable for pediatric patients, then undergoes parameter change through thermal activation. Heating the stent with warm saline (e.g., 40-50°C) triggers the shape memory alloy to transform from austenite to martensite phase, generating sufficient radial force despite the stent's small initial size, thereby resolving the contradiction between small delivery size and sufficient expansion force
Solution Approach 2:
The stent deployment involves periodic thermal cycles where warm saline is infused to heat the stent in stages. This periodic heating allows controlled phase transformation and gradual radial expansion, enabling the stent to generate adequate force progressively rather than instantaneously, ensuring both safe delivery in small patients and sufficient expansion force
3Length of stationary object
If a stent is designed to expand to a large diameter to treat adult aortas, then the stent can treat aortic coarctation in adult patients, but the stent cannot accommodate vessel growth in pediatric patients
Solution Approach 1:
The stent is designed with dynamic expandability through shape memory alloy properties, allowing it to transition between multiple diameter states. The stent can be delivered in a compact state, expanded to an intermediate diameter for pediatric patients, and potentially re-heated and expanded further as the patient grows, providing adaptability across different growth stages without requiring replacement
Solution Approach 2:
The stent structure is designed to serve multiple functions and patient populations. A single stent design can treat both pediatric and adult patients by adjusting the expansion degree through controlled thermal activation. The stent's universal design allows it to function as both a growth-accommodating pediatric stent and an effective adult stent, eliminating the need for different stent types for different age groups
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 stent effectively widens the aorta, reduces the need for repeated interventions, and is suitable for pediatric patients by maintaining the vessel open without causing damage, addressing the limitations of existing treatments by providing a self-expanding solution that adapts to vessel growth.
Implementation Method 1
made from materials like Nitinol for shape-memory properties, allowing for deployment in small patients and continued expansion with patient growth
Implementation Method 2
configured to produce an outward radial force with the stent having a diameter greater than or equal to a compact diameter and less than or equal to a fully expanded diameter, the outward radial force depending at least in part on the wall thickness of individual struts and configured to be sufficient to resist elastic recoil for aortic coarctation in a subject
Data Source
AI summary
Described herein are radially self-expanding stents. The disclosed stents can be used to widen arteries and/or veins of a patient to counteract or combat narrowing of the arteries and/or veins associated with certain congenital diseases, such as aortic coarctation. As an example, the disclosed stents are configured to be placed at or near a narrowed portion of the aorta where the stent produces a radial outward force on the aorta. The radial force produced by the stent widens the aorta and causes the stent to expand with the aorta. The disclosed stents can be crimped to relatively small sizes for placement in small patients (e.g., less than about 10 kg in size) and can be configured to expand to widen the aorta and to accommodate growth in the patient.