Selective Vagus Nerve Stimulation via Pulse Train Segmentation
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Solution Overview
Problem
Current vagus nerve stimulation (VNS) devices for congestive heart failure (CHF) often cause side effects like voice hoarsening, coughing, and neck pain due to unwanted recruitment of large-diameter fibers, which can be minimized by selectively stimulating parasympathetic cardiac fibers while avoiding large-diameter fibers that innervate the pharynx and larynx.
Innovation Solution
An implantable pulse generator (IPG) connected to a multi-contact nerve cuff electrode delivers a pulse train with an initial selective-arrest phase for large-diameter fibers, followed by a charge-balanced Alternating Current (AC) phase that is briefly unbalanced to deliver therapy pulses, using a low-Q Class-E switched amplifier and quasi-trapezoidal pulse envelope to selectively stimulate vagus nerves, thereby minimizing recruitment of large-diameter fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard VNS stimulation is applied to the vagus nerve, then cardiovascular therapeutic effects are achieved, but large-diameter fibers innervating the pharynx and larynx are also stimulated causing side effects
Solution Approach 1:
The patent segments the stimulation waveform into distinct phases: a selective-arrest phase that specifically targets and arrests large-diameter fibers, followed by a therapy phase that stimulates smaller cardiac fibers. This temporal segmentation allows differential control over fiber types, achieving cardiovascular effects while minimizing side effects from laryngeal and pharyngeal fiber activation.
Solution Approach 2:
The selective-arrest phase is applied as a preliminary action before the main therapy phase. By first arresting large-diameter fibers through a brief high-amplitude pulse, the patent prevents these fibers from being recruited during subsequent therapy delivery, thereby preemptively eliminating the source of side effects before therapy begins.
2Reliability
If charge-balanced AC is continuously applied, then nerve fiber selectivity is maintained, but therapy pulse delivery is limited
Solution Approach 1:
The patent employs periodic action by delivering therapy pulses as intermittent unbalancing events within the charge-balanced AC framework. The AC waveform alternates between charge-balanced operation (maintaining selectivity) and brief unbalanced phases (delivering therapy), creating a rhythmic pattern that reconciles the conflicting requirements of fiber selectivity and therapy delivery efficiency.
Solution Approach 2:
The patent dynamically changes waveform parameters by temporarily unbalancing the charge-balanced AC waveform during therapy pulse delivery. This parameter change allows the system to switch between two operational modes: charge-balanced mode for maintaining fiber selectivity and unbalanced mode for delivering therapeutic current, with the ability to transition between modes as needed.
Data Source
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AI summary
The invention concerns an implantable pulse generator (106) that is connected or can be connected to a stimulation lead (100) having a plurality of stimulation electrodes (102, 104) for delivery of stimulation pulses. The implantable pulse generator (106) comprises at least one stimulation unit (36, 38, 40, 42, 44, 46) that is configured to generate electric stimulation pulses for nerve stimulation. The implantable pulse generator (106) further comprises a control unit (50) that is configured to trigger delivery of generated electric stimulation pulses via selected electrodes of the plurality of stimulation electrodes (102, 104) wherein said electric stimulation pulses form a pulse train comprising: i) an initial selective-arrest phase for the large-diameter fibers in the vicinity of selected electrodes; ii) followed by a phase where a charge-balanced alternating current (AC) is applied between the same or other selected electrodes; iii) and where such AC is briefly unbalanced to effectively deliver nerve stimulation therapy pulses, returning to charge-balanced operation in between therapy pulses.