Expandable Nitinol Basket for Clot Retrieval Without Vessel Occlusion
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Solution Overview
Problem
Current intravascular thrombus removal devices are ineffective in removing hard, organized blood clots and foreign bodies from the brain due to their design limitations, such as requiring vessel occlusion, failing to dislodge clots from vessel walls, and causing embolization of clot fragments during retrieval.
Innovation Solution
A deployable system comprising a catheter-delivered device with a distal body made of memory metal strips that can expand to capture and retrieve clots without occluding the vessel, featuring a pull wire mechanism and a basket design that allows for the capture and removal of clots without fragmenting them, and can be manufactured from a single nitinol tube to fit within small catheters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current thrombus removal devices are used, then device delivery is possible through catheters, but the devices fail to effectively remove hard organized clots and cause embolization of clot fragments
Solution Approach 1:
The device divides the clot capture function into multiple segments: the expandable basket structure with multiple wires that can independently engage with the clot, and the separate filter component that captures fragmented material. This segmentation allows the device to handle both large organized clots and small fragments without causing embolization.
Solution Approach 2:
The device introduces an intermediary filtering mechanism between the clot retrieval process and the bloodstream. The filter component acts as a mediator that intercepts and captures clot fragments before they can embolize, while the basket structure mediates the engagement with the main clot body for safe retrieval.
2Reliability
If vessel occlusion is used to retrieve clots, then clot capture is possible, but blood flow is blocked causing further ischemia and vessel injury
Solution Approach 1:
The device applies local quality by creating a focused capture zone at the distal end where the expandable basket and filter are positioned. Only the local area where the clot resides is affected by the retrieval mechanism, while the rest of the vessel maintains normal blood flow. The device engages the clot locally without requiring proximal occlusion.
Solution Approach 2:
Instead of occluding the vessel proximally and retrieving the clot by pulling back (the conventional approach), this device inverts the approach by positioning the capture mechanism distally at the clot site and retrieving by withdrawing the device while maintaining open proximal flow. This inversion eliminates the need for proximal occlusion and its associated harms.
3Ease of operation
If the device is made small and flexible to navigate tortuous vessels, then vessel navigation is possible, but the device lacks strength to dislodge strongly adherent thrombus
Solution Approach 1:
The device employs dynamics by using an expandable structure that transitions from a compact delivery configuration to an expanded retrieval configuration. The basket wires and filter structure are compressed during navigation through tortuous vessels, then expanded at the target site to generate sufficient strength for dislodging adherent thrombus. This dynamic transformation allows the device to achieve both navigability and strength.
Solution Approach 2:
The device uses nesting by placing the expandable basket structure and filter within a delivery catheter in a compressed state. Once positioned at the clot site, the structure is deployed outward from the catheter, expanding the capture elements. This nested configuration allows the strong retrieval structure to be delivered through small catheters while maintaining the capability to exert sufficient force on the clot.
4Reliability
If the device is designed to completely remove occlusion, then clot retrieval is achieved, but the device complexity increases requiring multiple components
Solution Approach 1:
The device merges two functions into a single integrated structure: the expandable basket for capturing the main clot body and the filter for capturing fragmented material. Both functions are combined in one deployable unit that works together to achieve complete clot removal. The pull wire mechanism also serves dual purposes of controlling basket expansion and facilitating device retrieval.
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 system effectively removes hard clots and foreign bodies from blood vessels without occluding the vessel, reduces embolization risk, and is easy to use and manufacture, providing a safe and efficient method for clot retrieval.
Implementation Method 1
a distal body made of memory metal strips that can expand to capture and retrieve clots
Data Source
AI summary
Catheter-delivered endovascular medical devices are described. The devices may include a pull wire attached to a deployable basket. The basket may include a proximal portion comprising proximal cells defined by a plurality of basket strips and a distal portion comprising a plurality of distal braided mesh openings formed by a plurality of woven linear strands. The proximal and distal portions may overlap with the distal portion being in the proximal portion interior. The distal braided mesh openings may be smaller than the proximal cells when the device is in the relaxed state. Methods of using and making the devices are also described.