Phrenic Nerve Detection via Dual Filter Channels
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Solution Overview
Problem
Cardiac pacing therapies often unintentionally stimulate the phrenic nerve, leading to inefficient cardiac output due to the inability to accurately detect and avoid phrenic nerve activation, especially during cardiac pacing therapy.
Innovation Solution
An implantable medical device with a pulse generator and sensors that use separate filter channels to detect phrenic nerve activation by filtering accelerometer and respiration signals, allowing for the determination of phrenic nerve activation and adjustment of pacing parameters to avoid nerve stimulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cardiac pacing therapy is delivered to improve cardiac output, then cardiac pumping efficiency is improved, but unintentional phrenic nerve stimulation occurs causing patient discomfort and reduced therapy effectiveness
Solution Approach 1:
The system performs preliminary detection of phrenic nerve activation by monitoring accelerometer signals and respiration patterns before adjusting pacing parameters. This allows the system to proactively identify when phrenic nerve stimulation is occurring and prevent it by modifying pacing therapy in advance, rather than reacting after the stimulation has already caused discomfort.
Solution Approach 2:
The system continuously monitors patient responses to pacing therapy using accelerometers and respiration sensors, and uses this feedback to dynamically adjust pacing parameters. When phrenic nerve activation is detected through characteristic motion patterns or respiration changes, the system feeds this information back to modify the pacing therapy to avoid further stimulation while maintaining effective cardiac output.
2Reliability
If pacing pulse energy is increased to ensure reliable cardiac capture, then cardiac tissue capture is improved, but phrenic nerve activation threshold is exceeded causing unwanted nerve stimulation
Solution Approach 1:
The system dynamically adjusts pacing pulse energy based on real-time detection of phrenic nerve activation risk. Rather than using fixed high energy levels, the pacing parameters are continuously modified according to patient response and detected nerve activation patterns, allowing the system to use the minimum necessary energy to achieve reliable cardiac capture without exceeding phrenic nerve activation thresholds.
Solution Approach 2:
The system changes pacing parameters such as pulse amplitude, duration, and timing to optimize cardiac capture while avoiding phrenic nerve stimulation. By modifying these parameters dynamically based on detected patient responses and nerve activation indicators, the system maintains reliable cardiac capture at lower energy levels that do not trigger unwanted phrenic nerve activation.
3Measurement precision
If separate filter channels are used to detect phrenic nerve activation, then detection precision is improved, but device complexity increases
Solution Approach 1:
The system uses multi-functional signal processing circuitry that serves both activity monitoring and phrenic nerve activation detection purposes. The same accelerometer and respiration sensors are processed through filter channels that can identify both general patient activity levels and specific phrenic nerve activation patterns, reducing the need for separate dedicated detection hardware while maintaining high detection precision.
Solution Approach 2:
The signal processing is divided into separate filter channels that process different frequency ranges or signal characteristics independently. This segmentation allows the system to detect phrenic nerve activation by analyzing specific signal features in dedicated channels while using other channels for general activity monitoring, improving detection precision through specialized processing without requiring completely separate hardware systems.
Data Source
AI summary
An implantable cardiac device includes a sensor for sensing patient activity and detecting phrenic nerve activation. A first filter channel attenuates first frequencies of the sensor signal to produce a first filtered output. A second filter channel attenuates second frequencies of the accelerometer signal to produce a second filtered output. Patient activity is evaluated using the first filtered output and phrenic nerve activation caused by cardiac pacing is detected using the second filtered output.