Variable-Braid Delivery Tube for Aortic Valve Navigation
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Solution Overview
Problem
Current ventricular assist devices face challenges in efficiently navigating the aortic valve and arch due to rigid delivery tubes, which can lead to complications during implantation and operation, and there is a need for a solution that allows for varying mechanical properties along the tube length to facilitate smooth passage and optimal blood pumping.
Innovation Solution
A left-ventricular assist device with a delivery tube that has varying flexural rigidity along its length, specifically designed to traverse the aortic valve, arch, and descending aorta, using a combination of materials and structures such as a braid with varying pick density and a coil with varying pitch, along with an outer layer of different materials like polyurethane and polyether block amide, to ensure optimal mechanical properties for each section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid delivery tube is used, then the structural strength and support are improved, but the ability to navigate the aortic valve and arch is worsened
Solution Approach 1:
The delivery tube is designed with non-uniform braid construction where the pick density varies along its length. Specifically, the pick density is higher in sections requiring greater flexural rigidity (such as the proximal portion) and lower in sections requiring greater flexibility (such as the distal portion). This local variation in structural properties allows the tube to maintain overall strength while providing localized flexibility for navigating anatomical structures like the aortic valve and arch.
Solution Approach 2:
The invention changes the physical parameter of flexural rigidity along the length of the delivery tube by varying the braid pick density. This creates a gradient in mechanical properties where the tube transitions from stiffer proximal sections to more flexible distal sections, enabling the tube to bend and conform to the curved anatomy of the aorta while maintaining sufficient structural integrity.
2Ease of operation
If a flexible delivery tube is used, then the ability to navigate the aortic valve and arch is improved, but the structural strength and support are worsened
Solution Approach 1:
The delivery tube employs non-uniform braid construction with spatially varying pick density to achieve optimal balance between flexibility and strength. The proximal portion has higher pick density for structural support, while the distal portion has lower pick density for navigation flexibility, resolving the contradiction between these two requirements.
Solution Approach 2:
The delivery tube uses a composite structure combining braided reinforcement with a tubular body material. The braided layer provides tensile strength and structural support, while the base tube material provides flexibility and compliance. This composite construction allows the tube to simultaneously achieve both strength and flexibility.
3Ease of manufacture
If uniform braid pick density is used, then manufacturing simplicity is improved, but the ability to provide varying mechanical properties along the tube length is worsened
Solution Approach 1:
The braid is constructed with non-uniform pick density where the number of picks per inch varies along the length of the delivery tube. This allows different sections to have tailored mechanical properties - higher pick density for strength-critical areas and lower pick density for flexibility-critical areas - while still being manufacturable using standard braiding techniques with programmable tension control.
Data Source
AI summary
Apparatus and methods are provided, including inserting an impeller and a delivery tube into a subject's body, the delivery tube including a braid having a pick density that varies along the delivery tube's length such that a flexural rigidity of the delivery tube at a first portion of the delivery tube is less than the flexural rigidity at a second portion of the delivery tube, and the flexural rigidity at the second portion is less than the flexural rigidity at a third portion of the delivery tube. The impeller and delivery tube are positioned such that the impeller is disposed within the subject's left ventricle and the delivery tube passes the subject's aorta into the left ventricle. Using a drive cable, which passes through the delivery tube, the impeller is rotated so as to pump blood from the left ventricle into the aorta. Other applications are also described.