Buckling Catheter Sidewall for Pacemaker Retrieval
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Solution Overview
Problem
Current systems for retrieving implantable cardiac pacemakers from implant sites face challenges related to mechanical and MRI compatibility, requiring new tools and methods to enhance ease and efficiency of retrieval.
Innovation Solution
A catheter with a device receptacle having a buckling sidewall structure, where the central section is less stiff than the proximal and distal sections, allowing alignment and retrieval of the pacemaker, and a fixation member with elastically deformable fingers to secure the device during retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional elongate lead wire pacemaker is implanted, then reliable pacing function is achieved, but mechanical compatibility issues and MRI compatibility issues arise
Solution Approach 1:
The pacemaker is segmented into distinct functional components: a header portion containing electronic circuitry and a separate electrode portion with fixation fingers. This segmentation allows the electrode to be independently optimized for tissue engagement while the header maintains electrical connectivity, resolving the contradiction between reliable pacing function and mechanical/MRI compatibility by separating the functions that cause compatibility issues from the essential pacing function.
Solution Approach 2:
The fixation fingers are nested within the header portion during delivery and deployment, then extend outward to engage tissue. This nested configuration allows the device to be delivered through small vasculature without external wiring (improving MRI compatibility) while still providing reliable tissue fixation and pacing function.
2Object-affected harmful factors
If a compact implantable pacemaker is used, then mechanical and MRI compatibility are improved, but retrieval difficulty increases
Solution Approach 1:
The fixation fingers are pre-configured in a compressed state within the header during delivery. Upon deployment, they automatically expand and engage the tissue, creating a secure anchor that facilitates later retrieval. This preliminary compression and subsequent expansion creates a retrieval mechanism that works with the compact device design rather than against it.
Solution Approach 2:
The fixation fingers transition from a static compressed state during delivery to a dynamic extended state during implantation and retrieval. This dynamic behavior allows the same structure to serve multiple functions: compact delivery for MRI compatibility, secure fixation for reliable operation, and controlled expansion for easy retrieval.
3Reliability
If fixation fingers are made rigid for secure tissue engagement, then fixation reliability is improved, but ability to navigate through catheter decreases
Solution Approach 1:
The fixation fingers are designed as elastic elements that dynamically change their mechanical properties based on their state. During delivery, they are compressed and flexible, allowing easy navigation through the catheter. Upon deployment, they extend and become rigid through elastic recovery, providing secure tissue fixation. This dynamic transition resolves the contradiction between navigability and fixation reliability.
Solution Approach 2:
The mechanical parameters of the fixation fingers (stiffness, shape) are changed through elastic deformation. In the compressed state, the fingers have low stiffness for catheter navigation. In the extended state, elastic recovery increases their stiffness for reliable tissue engagement. This parameter change through elastic deformation allows the same structure to satisfy both contradictory requirements.
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
Facilitates efficient retrieval of implanted devices by aligning the catheter opening with the pacemaker and securing it with deformable fingers, improving the ease and efficiency of the retrieval process.
Implementation Method 1
causing the central section of the device receptacle sidewall to buckle so that the a central axis of the distal opening of the chamber defined by the sidewall becomes approximately aligned with a longitudinal axis of the device at the implant site
Implementation Method 2
a fixation member mounted to the distal end of the housing, the fixation member comprising a plurality of fingers spaced apart from one another around a perimeter of the distal end of the housing, each finger being elastically deformable between a relaxed condition and an extended condition
Data Source
AI summary
A device receptacle of a catheter resides in a sidewall thereof, which includes a proximal section, a central section extending distally from the proximal section, and a distal section extending distally from the central section. A length of the central section is approximately 30% of an overall length of the sidewall; the proximal and distal sections have approximately the same stiffness; and a stiffness of the central section, formed from a polymer material without any structural reinforcement or any other member embedded therein, is significantly less than that of the proximal and distal sections. When an operator causes the receptacle sidewall to buckle, a distal opening of a chamber of the receptacle becomes aligned with an implanted device so that the operator can bring the implanted device into the chamber to retrieve the device from the implant site.