Biased Ring Electrode for Directional Stimulation Field Control
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Solution Overview
Problem
Implantable medical leads often face challenges in controlling the direction of stimulation fields, particularly during cardiac pacing and neurostimulation, where undesired nerve or muscle stimulation can occur, such as phrenic nerve stimulation during left ventricle pacing and neck muscle stimulation during vagal neurostimulation.
Innovation Solution
The use of biased ring electrodes with varying widths along the longitudinal direction of the lead body, which directs the stimulation field in a specific radial or transverse direction, allowing for targeted tissue stimulation while minimizing unwanted nerve or muscle stimulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a ring electrode with even width is used, then the stimulation field is distributed equally about the perimeter of the lead, but this causes undesired stimulation of adjacent nerves or muscles (e.g., phrenic nerve during LV pacing, neck muscles during vagal neurostimulation)
Solution Approach 1:
The patent applies asymmetry by designing a ring electrode with non-uniform width around its perimeter. Specifically, the electrode has a greater width on one side than on the opposite side, creating an asymmetric geometry that biases the stimulation field in a predetermined direction. This asymmetric design allows the stimulation field to be directed away from sensitive structures like the phrenic nerve or neck muscles, thereby reducing undesired stimulation while maintaining the simple ring electrode configuration.
Solution Approach 2:
The patent implements local quality by varying the width of the ring electrode at different locations around its perimeter. The electrode width is specifically increased on the side opposite to where undesired stimulation would occur, creating localized differences in electrical field distribution. This local modification of electrode geometry allows targeted control of the stimulation field direction without requiring complete redesign of the entire electrode structure.
2Object-affected harmful factors
If the lead is specifically positioned to avoid the phrenic nerve, then phrenic nerve stimulation is reduced, but the lead is positioned at a non-optimal site for LV pacing
Solution Approach 1:
The asymmetric ring electrode design enables the lead to be positioned in the optimal location for LV pacing (in the coronary sinus or coronary vein) without causing phrenic nerve stimulation. The biased geometry of the electrode directs the stimulation field away from the phrenic nerve while maintaining effective contact with the left ventricular myocardium, thus resolving the positioning conflict between optimal pacing site and avoidance of harmful nerve stimulation.
3Ease of manufacture
If ring electrodes are used as an alternative to cuff electrodes for vagal nerve stimulation, then the procedure is simplified, but neck muscles may also be stimulated which is generally undesirable
Solution Approach 1:
The patent applies asymmetry to the ring electrode design specifically for vagal nerve stimulation applications. The electrode width is biased to direct the stimulation field preferentially toward the vagal nerve while away from adjacent neck muscles. This asymmetric geometry maintains the procedural simplicity of using a ring electrode instead of a cuff electrode, while simultaneously reducing the harmful side effect of neck muscle stimulation through directional field control.
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
This approach effectively biases the stimulation field to avoid undesired tissue areas, ensuring precise delivery of therapy and reducing unwanted nerve or muscle stimulation, thereby improving the efficacy of cardiac pacing and neurostimulation treatments.
Implementation Method 1
the width of the ring electrode as measured along the longitudinal direction of the lead may vary about the perimeter of the lead... the stimulation field may be biased toward the portion or 'side' of the lead body where the electrode has an increased surface area
Data Source
Figure 1
Figure 2A~2B
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AI summary
This disclosure describes implantable medical leads that include a lead body and an electrode. A width of the electrode as measured along a longitudinal direction of the lead varies about the perimeter of the lead. The uneven width of the electrode may bias a stimulation field in a particular direction, e.g., a radial or transverse direction relative to the longitudinal axis of the lead. Electrodes with an uneven width may be useful for controlling the direction of propagation of the stimulation field in order to, for example, avoid phrenic nerve stimulation during LV pacing or neck muscle stimulation during vagal neurostimulation.