Implantable Cardiac Pacer Phrenic Nerve Stimulation Detection

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Solution Overview

Problem

Implanted pacing systems often cause unintended phrenic nerve stimulation due to the close proximity of pacing leads to the phrenic nerve, leading to discomfort and the need for additional medical interventions to reprogram or reposition leads, as the anatomic location of the phrenic nerve varies among patients and the veins for lead placement are not consistently aligned with the ventricle and nearby nerves.

Innovation Solution

An implantable medical device (IMD) equipped with a cardiac pace generator, phrenic nerve stimulation (PS) sensor, and a controller that performs a PS detection procedure, including a trigger module, recognition module, PS test module, and decision module, to automatically detect and confirm PS, adjust pacing configurations, or alert external devices to minimize unwanted stimulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LV pacing is used to treat heart failure, then cardiac resynchronization therapy is achieved, but unintended phrenic nerve stimulation occurs causing diaphragm contraction and patient discomfort

Engineering Contradiction:

Improvecardiac resynchronization therapy effectivenessVSAvoidphrenic nerve stimulation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary phrenic nerve stimulation detection during device implantation and follows-up visits by analyzing accelerometer signals. This early detection allows clinicians to identify patients at risk before discomfort becomes severe, enabling proactive adjustment of pacing parameters or lead positioning to prevent the harmful effect while maintaining therapeutic benefit

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors accelerometer data to detect diaphragm motion patterns indicative of phrenic nerve capture. When PS is detected, the system provides feedback to clinicians through stored events and waveforms, enabling adjustment of pacing parameters. This closed-loop feedback mechanism allows optimization of pacing therapy to avoid harmful stimulation while maintaining effective cardiac resynchronization

Inventive Principle:

Principle #23Feedback

2Reliability

If phrenic nerve stimulation is detected at implant, then lead positioning can be adjusted, but unintended PS may first appear or worsen post-implant requiring additional office visits or surgical repositioning

Engineering Contradiction:

Improvephrenic nerve stimulation assessmentVSAvoidadditional office visits and surgical repositioning

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system automatically and continuously monitors for phrenic nerve stimulation using the accelerometer without requiring manual patient reporting or frequent clinical assessments. The device autonomously detects diaphragm motion, stores PS events with associated waveforms, and makes pacing parameter adjustments to prevent PS, reducing the need for additional office visits and surgical interventions

Inventive Principle:

Principle #25Self-service

3Power

If the electric field of the LV pacing lead is strong enough to capture the phrenic nerve, then pacing output is effective, but unintended phrenic nerve activation causes hiccups and discomfort

Engineering Contradiction:

Improvepacing output strengthVSAvoidphrenic nerve capture

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The system uses accelerometer monitoring to detect partial diaphragm activation that may precede full phrenic nerve capture. By detecting these early signs through continuous acceleration analysis, the system can adjust pacing parameters preventively, allowing effective pacing output while avoiding the harmful threshold of full phrenic nerve activation that causes symptomatic hiccups

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system dynamically adjusts pacing parameters including amplitude, pulse width, and vector based on detected phrenic nerve stimulation patterns. By changing these parameters, the system maintains effective cardiac pacing while reducing the electric field strength or direction that causes harmful phrenic nerve capture, thereby eliminating symptoms while preserving therapeutic effect

Inventive Principle:

Principle #35Parameter changes

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 system reduces patient discomfort and clinical burden by accurately and automatically detecting unintended phrenic nerve stimulation, allowing for timely adjustments to pacing configurations and reducing the need for repeated medical visits or surgeries.

Implementation Method 1

an accelerometer sensor for phrenic nerve stimulation (PS) detection

Methodology Applied

Scientific EffectAccelerometer detection: Accelerometer

Data Source

PatentUS11471688B2Ambulatory phrenic nerve stimulation detection

Publication Date: 2022.10.18 CARDIAC PACEMAKERS INC

AI summary

An example of a system includes an implantable medical device (IMD) for implantation in a patient, where the IMD includes a cardiac pace generator, phrenic nerve stimulation (PS) sensor, a memory, and a controller, and where the controller is operably connected to the cardiac pace generator to generate cardiac paces. The controller is configured to provide a trigger for conducting a PS detection procedure and perform the PS detection procedure in response to the trigger. In performing the PS detection procedure the controller is configured to receive a signal from the sensor, detect PS using the signal from the sensor, and record the PS detection in storage within the IMD.