Helical Welded Atherectomy Cutting Member
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Solution Overview
Problem
Current atherectomy devices face challenges in effectively removing occlusive material from blood vessels without damaging the surrounding vessel wall or previously implanted stents, and in efficiently handling both hard and soft occlusive materials.
Innovation Solution
The design of an atherectomy device featuring an elongate shaft with a drive coil and a cutting member secured by a strain relief member, where the cutting member has a unique outer surface geometry and is welded to the shaft with helical welds that reduce stress concentration and facilitate secure attachment, allowing for effective excision of occlusions without damaging the vessel or stents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cutting member is secured to the elongate shaft using conventional welding methods, then the cutting member is attached to the shaft, but stress concentration occurs at the weld points which can lead to device failure or damage to the vessel wall
Solution Approach 1:
The welds are configured to extend helically around the drive coil rather than in a straight line, distributing the stress across multiple dimensions and locations. This helical configuration transforms the stress distribution from a concentrated linear pattern to a distributed three-dimensional pattern, reducing peak stress concentrations at any single point.
Solution Approach 2:
The welding process creates multiple discrete weld points distributed along the helical path rather than a single continuous weld. This segmentation divides the stress load across numerous small weld points, preventing stress concentration at any one location while maintaining overall attachment integrity.
2Ease of manufacture
If the cutting member is made with a simple geometry, then the device is easier to manufacture, but it cannot effectively handle both hard and soft occlusive materials
Solution Approach 1:
The cutting member features an asymmetric geometry with a larger radius of curvature on one side and a smaller radius on the other side. This local variation in geometric quality allows different portions of the cutting surface to interact differently with occlusive material, enabling effective cutting of both hard and soft materials while maintaining a relatively simple overall structure that can be manufactured using standard techniques.
Solution Approach 2:
The cutting member's outer surface incorporates varying radius of curvature parameters along its geometry. By changing the curvature parameter locally rather than maintaining a uniform radius, the cutting member gains the ability to adapt to different material hardness levels, achieving versatility without requiring multiple different cutting members.
3Volume of moving object
If the drive coil has tight windings to reduce device diameter, then the device profile is smaller for better vessel access, but stress concentration increases at the coil windings
Solution Approach 1:
The welds extend in a helical direction that is angled relative to the coil windings, creating a three-dimensional stress distribution pattern. This angular configuration allows the welds to bridge across multiple coil windings in a staggered pattern, distributing mechanical stresses away from any single winding point and reducing stress concentration despite tight coil spacing.
4Device complexity
If conventional atherectomy devices are used, then the device structure is simpler, but they cannot effectively excise occlusions without damaging the vessel wall or stents
Solution Approach 1:
The cutting member's outer surface is configured with a specific asymmetric geometry featuring varying radius of curvature. This geometric parameter optimization allows the cutting member to engage and excise occlusive material more selectively and controllably, reducing the risk of uncontrolled cutting that could damage the vessel wall or stents, while the overall device structure remains relatively simple.
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 device effectively excises occlusive material while minimizing damage to the vessel wall and stents, enabling efficient removal of both hard and soft occlusive materials, thereby improving revascularization outcomes.
Implementation Method 1
one or more helical welds that extend helically at least part way around the tubular member
Implementation Method 2
helical welds that reduce stress concentration and facilitate secure attachment
Implementation Method 3
A cutting member is secured to the strain relief member and defines an outer surface
Data Source
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AI summary
Medical devices and methods for using medical devices are disclosed. A rotational atherectomy device may include an elongate drive coil having a proximal end region and a distal end region, the elongate drive coil having a coil winding extending in a first helical direction, the elongate drive coil having a coil pitch. A tubular member is welded to the distal end region of the elongate drive coil via one or more helical welds that extend helically at least part way around the tubular member and a cutting member welded to the tubular member.