Helical Multi-Strand Cable Fatigue Resistance in Pacing Leads

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

New pacing and defibrillation leads with multi-strand cables are prone to premature fatigue failure due to bending stress, especially at sharp bends, leading to increased failure rates as the number of conductor cables increases.

Innovation Solution

A pacing and defibrillation lead design featuring a tubular body with a flex-strain relief segment that includes a highly flexible core with multi-strand cable conductors routed helically, decoupling them from normal bending strains, and a strain-flex relief assembly with radially extending members to maintain the conductors in a helical configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multi-strand cable conductors are used as primary conductors in leads, then the electrical conductivity and current carrying capacity are improved, but the leads become prone to premature fatigue failure due to bending stress

Engineering Contradiction:

Improvefatigue resistanceVSAvoidresistance to bending stress

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The lead is divided into distinct segments: a rigid body portion for structural support and electrical connectivity, and a flexible portion with helically wound conductors for strain relief. This segmentation allows each portion to optimize its function - the rigid portion provides strength while the flexible portion with helical conductors accommodates bending without fatigue failure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cable conductors are configured in a helical winding rather than a straight parallel arrangement. This dynamic configuration allows the conductors to flex and expand during bending, absorbing mechanical stress through the helical geometry's natural ability to accommodate dimensional changes without creating fatigue points.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the number of conductor cables in a lead is increased, then the electrical performance is improved, but the incidence of primary conductor failure due to bending stress increases

Engineering Contradiction:

Improveconductor durabilityVSAvoidnumber of conductor cables

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple cable conductors are merged into a single helical winding structure rather than remaining as separate parallel cables. This combining approach maintains the electrical functionality of multiple conductors while the unified helical structure provides collective strain relief, reducing the overall incidence of conductor failure even as the number of conductors increases.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If cable conductors are routed in a non-helical configuration, then the manufacturing process is simpler, but the conductors are subject to stretching and compressing during lead flexing

Engineering Contradiction:

Improveconductor routingVSAvoidresistance to stretching and compressing

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS7680544B1Fatigue resistant design for leads employing multi-strand cables as primary conductors

Publication Date: 2010.03.16 PACESETTER INC

AI summary

A lead for connecting to a pacing and/or defibrillation power source is disclosed herein. The lead includes a lead tubular body, a connector for connecting the lead to the power source, and a strain-flex relief assembly joining the lead tubular body to the connector assembly and including a helical multi-strand cable conductor configuration.