Stranded Tether Cable for Biostimulator Delivery Fatigue
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Solution Overview
Problem
Existing leadless biostimulator delivery systems face issues with tether material fatigue due to bending stresses during deployment, leading to potential breakage and loss of the device within the patient anatomy.
Innovation Solution
A biostimulator delivery system featuring a tether cable with a stranded configuration, including a core strand surrounded by helically wrapped side strands, which reduces bending stresses and enhances flexibility and fatigue resistance, along with a retaining coil to maintain tether alignment and prevent misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a continuous wire tether is used to attach the biostimulator to the delivery system, then the tether can be manufactured with a simple grinding process, but the tether experiences substantial bending stresses that can cause fatigue failures and breakage
Solution Approach 1:
The tether is segmented into multiple individual wires (e.g., 7-19 wires) bundled together to form a cable. This segmentation allows each wire to independently accommodate bending stresses through rotational movement within the bundle, significantly reducing fatigue accumulation compared to a single continuous wire. The segmented structure maintains manufacturing feasibility while dramatically improving fatigue resistance and reliability under cyclic bending loads.
Solution Approach 2:
The tether employs a composite cable structure combining multiple wire materials (e.g., nickel-titanium alloy, cobalt-chromium alloy, or stainless steel) with different mechanical properties. This composite approach allows optimization of each wire's contribution to flexibility, strength, and fatigue resistance, creating a tether that withstands bending stresses better than any single material could achieve alone.
2Ease of operation
If the tether assembly supports the biostimulator freely in tether mode without catheter support, then the biostimulator can be positioned and released at the target anatomy, but the tether experiences substantial bending stresses from heart movements
Solution Approach 1:
The tether is designed as a dynamic, flexible cable rather than a rigid rod, allowing it to adapt its configuration in response to heart movements and catheter manipulation. The individual wires within the cable can rotate and reposition relative to each other, enabling the tether to dynamically absorb bending stresses while maintaining its load-bearing capacity during the tether mode operation and biostimulator release sequence.
Solution Approach 2:
The tether's effective stiffness and flexibility parameters are optimized through selection of wire material properties, diameter, and bundle configuration. This allows the tether to exhibit appropriate mechanical characteristics during different phases of deployment - sufficiently flexible to accommodate heart movements and catheter navigation, yet strong enough to support the biostimulator weight and resist breakage during tether mode operation.
Data Source
AI summary
A biostimulator delivery system having a tether cable, is described. A connector can be mounted on the tether cable to connect to a biostimulator. The connector can be a protuberance that lodges within the biostimulator, or a threaded connector that screws into the biostimulator. The tether cable has a stranded cable configuration, including several strands extending about a core strand in a helical direction. The stranded cable structure resists breaking under bending stresses typically seen during a tether mode used during delivery of the biostimulator. The tether cable reliably secures the biostimulator to the delivery system in the tether mode. Other embodiments are also described and claimed.