Lead Bore Seal Geometry for Electrical Isolation Under Lead Movement
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Solution Overview
Problem
Existing seals in implantable medical devices fail to provide adequate electrical isolation due to movement-induced fluid ingress and debris accumulation, which can lead to signal leakage, especially when sensing small neurological signals amidst large cardiac signals.
Innovation Solution
A seal design featuring a cylindrical portion that contacts the lead body over a longer length with low average contact pressure, using an elastic seal body with a first cylinder and wall portion, allowing for movement while maintaining electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal with radially inward protrusions is used to contact the lead body, then electrical isolation is provided, but high contact pressure is required which increases insertion force and allows fluid ingress when the lead moves
Solution Approach 1:
The patent changes the contact pressure parameter by using a compliant material with durometer of 20A-90A that can deform under low pressure to maintain sealing contact. This allows the seal to provide adequate electrical isolation while requiring significantly lower insertion forces compared to rigid protrusion-based seals.
Solution Approach 2:
The patent employs a flexible cylindrical seal body that can deform radially to maintain contact with the lead body. This flexibility allows the seal to accommodate lead body movement and radial expansion while maintaining continuous sealing contact, preventing fluid ingress without requiring high contact pressures.
2Reliability
If a seal with fixed position protrusions is used, then electrical isolation is achieved, but the seal cannot accommodate lead body movement which creates gaps for fluid ingress
Solution Approach 1:
The patent implements a dynamic seal where the cylindrical body can deform radially in response to lead body movement. The seal transitions from a static fixed-position protrusion design to a dynamic compliant structure that continuously adapts its shape to maintain sealing contact during implantation and normal body movement.
Solution Approach 2:
The flexible cylindrical seal body with durometer 20A-90A allows the seal to deform and conform to lead body movement while maintaining continuous contact. This flexibility enables the seal to accommodate radial expansion and positional changes of the lead body without creating gaps that would allow fluid ingress.
3Reliability
If high contact pressure is used to prevent fluid ingress, then sealing is improved, but debris cannot be accommodated and signal leakage may occur
Solution Approach 1:
The patent changes the contact pressure parameter to low levels, utilizing the compliant material properties instead of high pressure to achieve sealing. This low-pressure approach prevents debris from being forced into the seal-lead interface, eliminating a potential source of signal leakage while maintaining effective sealing against fluid ingress.
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 seal effectively prevents signal leakage by maintaining electrical isolation even with debris present, reducing fluid ingress and accommodating lead movement, thus ensuring reliable signal delivery and sensing.
Implementation Method 1
an elastic seal body with a first cylinder defining a seal bore having a centerline
Data Source
AI summary
Seals used within lead bores of implantable medical devices for creating a seal to implantable medical leads inserted into the lead bores include a cylinder that engages the lead body. The length of contact of the cylinder to the lead body is at least 0.010″ long while average contact pressure is no greater than (10 pounds per inch)/(contact length). Adequate electrical isolation is achieved, even when a debris particle is present between the inner cylinder and the lead body while insertion force remains acceptable.