Variable Stiffness Microcatheter for Navigating Tortuous Vessels
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Solution Overview
Problem
Conventional microleads face challenges with 'pushability' and 'torquability', long-term implantability, and risk of compression or injury during manipulation, especially in small diameter venous, arterial, or lymphatic networks like the coronary sinus/coronary venous network, due to insufficient torsional stiffness and flexibility.
Innovation Solution
A microcatheter with a hollow tube structure featuring a decreasing stiffness gradient from the proximal to the distal region, made of biocompatible materials, and without reinforcing armor, allowing for navigability through tortuous vessels while providing 'pushability' and 'torquability' for implantation, with a distal region stiffness of no more than 0.09 N/mm and a ratio of proximal to distal stiffness between 2 and 10.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional microleads are made very flexible to navigate tortuous vessels, then navigability is improved, but torquability and pushability deteriorate due to insufficient torsional stiffness
Solution Approach 1:
The microlead is divided into multiple segments with different stiffness characteristics. The proximal segment has higher torsional stiffness for torquability, while the distal segment has lower stiffness for navigability. This segmentation allows each portion to optimize its mechanical properties for its specific function during navigation and implantation.
Solution Approach 2:
Different portions of the microlead are assigned different mechanical properties. The proximal end has enhanced torsional stiffness to transmit rotational movements, while the distal end has reduced stiffness to follow tortuous vessel paths. This local differentiation resolves the contradiction between overall flexibility and localized torquability.
2Ease of operation
If microleads are made smaller in diameter to reduce invasiveness, then ease of implantation is improved, but pushability and torquability deteriorate
Solution Approach 1:
The microlead employs variable stiffness parameters along its length. By changing the torsional stiffness parameter from proximal to distal, the lead maintains small diameter for ease of implantation while developing sufficient pushability and torquability where needed, resolving the size-strength contradiction.
3Strength
If guiding wires with high stiffness are used to provide pushability, then pushability is improved, but fatigue strength deteriorates making them unsuitable for permanent implants
Solution Approach 1:
The microlead uses variable stiffness parameters where the proximal portion has higher stiffness for pushability during implantation, while the distal portion has lower stiffness for navigability. This gradient design allows the lead to achieve pushability without requiring uniformly high stiffness throughout, thereby improving fatigue strength and reliability for permanent implantation.
Data Source
AI summary
This implantable microcatheter includes a hollow tube with a central lumen extending throughout the length of the tube from a proximal region to a distal region. The bending stiffness of the proximal region is greater than the bending stiffness of the distal region, and the tube has a transition region having a decreasing stiffness gradient from the proximal region to the distal region. The tube wall is free of shielding or armor at least in the distal region, and the catheter is made of biocompatible material(s) suitable for a permanent implantation in venous, arterial or lymphatic networks.