Cardiac Pacemaker Lead Sheath for Safe Extraction
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Solution Overview
Problem
Current methods for extracting cardiac pacemaker leads from veins are complicated and risk damaging the vein wall, leading to potential internal bleeding due to the use of rotary cutters to separate the lead from surrounding scar tissue.
Innovation Solution
A simplified sheath assembly is used over the pacemaker lead, which is formed from a single layer of material and secured to the lead. The sheath is designed to peel away from scar tissue when a tensile force is applied, allowing for easy extraction of the lead without damaging the vein wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rotary cutter is used to separate the lead from surrounding scar tissue, then the lead can be extracted from the vein, but the vein wall may be damaged or ruptured causing internal bleeding
Solution Approach 1:
A sheath is introduced as an intermediary protective layer between the lead and the vein wall. The sheath is designed to be separable from the scar tissue while protecting the vein wall from damage during extraction. This mediator approach allows the lead to be freed from encapsulating tissue without direct contact between extraction tools and the vein wall, thereby preventing rupture and bleeding.
Solution Approach 2:
The sheath is divided into multiple layers with distinct functions: an inner layer attached to the lead and an outer layer that interfaces with the scar tissue. The layers are connected through an annular fold that allows progressive separation. This segmentation enables the sheath to be peeled away from the lead in a controlled manner, facilitating extraction while protecting the vein wall from mechanical damage.
2Object-affected harmful factors
If a double layered sheath is used with a frangible seal to prevent blood seepage, then vein wall protection is improved, but assembly difficulty and manufacturing complexity increase
Solution Approach 1:
The complex frangible seal mechanism is extracted and replaced with a simpler alternative. Instead of using a seal that requires special assembly procedures, the invention uses the natural geometry of the sheath layers and the annular fold to create an effective barrier. The seal function is achieved through the structural design rather than through complex assembly features, thereby simplifying manufacturing while maintaining blood seepage prevention.
3Ease of manufacture
If a single layer sheath is used instead of double layered sheath, then manufacturing simplicity is improved, but extraction effectiveness may be reduced
Solution Approach 1:
The sheath is segmented into an inner layer attached to the lead and an outer layer that can be progressively separated from the scar tissue. This segmentation within a single-layer structure provides both the protection needed during implantation and the separability needed for extraction, achieving extraction effectiveness without requiring a complex double-layered design.
Solution Approach 2:
The sheath is designed with dynamic properties that allow it to transition from a protective covering during implantation to a separable structure during extraction. The annular fold and the relationship between inner and outer layers create a dynamic system that adapts to different operational phases, providing both manufacturing simplicity and extraction effectiveness.
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 solution enables safe and efficient extraction of cardiac pacemaker leads by simplifying the assembly process and reducing the risk of vein wall damage, thereby minimizing the risk of internal bleeding.
Implementation Method 1
The sheath is formed of an elastic material and is stretched when a tensile force is applied to the proximal end of the sheath. By Poisson's effect the region of the stretched sheath adjacent the nearest tissue is reduced in diameter resulting in separation or peeling of the sheath from the scar tissue
Implementation Method 2
By Poisson's effect the region of the stretched sheath adjacent the nearest tissue is reduced in diameter resulting in separation or peeling of the sheath from the scar tissue
Data Source
AI summary
A lead assembly for insertion into a body passage such as the lumen of a vein is particularly applicable for assembly of a cardiac pacemaker. In one version the lead has a distal end with an end portion of a flexible sheath attached with the sheath initially extending outwardly from the distal end and subsequently folded in an annular U-fold over the lead to provide a sheath along the length. By applying tensile force to the proximal end of the lead, the annular fold causes the material of the sheath to peel away from any surrounding scar tissue as the lead is pulled out towards the proximal end and provides for easy nondestructive extraction of the lead. In another version, a single layer flexible sheath is attached at the distal end of a lead, and, upon application of a tensile force to the stretchable sheath, the lead can be extracted.