Dynamic Sensing Threshold for Post-Shock Cardiac Event Detection
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Solution Overview
Problem
Current implantable medical devices (IMDs) face challenges in accurately sensing cardiac signals and controlling pacing pulses post-electrical stimulation, particularly after cardioversion or defibrillation shocks, which can lead to inappropriate therapy delivery and prolonged recovery times.
Innovation Solution
An implantable cardioverter defibrillator (ICD) system that senses cardiac electrical signals using an automatically adjusted post-pace cardiac event sensing threshold, allowing the escape interval timer to continue or reset based on sensed events, ensuring appropriate post-shock pacing pulse delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed sensing threshold is used after electrical stimulation, then the device structure remains simple, but the sensing accuracy deteriorates due to low-amplitude cardiac signals post-shock
Solution Approach 1:
The sensing threshold is made dynamic rather than fixed. The threshold automatically adjusts based on the timing relative to the electrical stimulation pulse, being higher immediately post-shock and gradually decreasing over time. This allows the system to adapt to changing signal conditions without requiring complex real-time analysis, resolving the contradiction between sensing accuracy and device complexity.
Solution Approach 2:
The sensing threshold parameter is changed over time according to a predetermined schedule following electrical stimulation. The threshold starts at a higher level to avoid oversensing of low-amplitude signals and gradually decreases to恢复正常 sensing sensitivity, allowing the system to maintain accuracy across different post-stimulation phases without complex control mechanisms.
2Reliability
If pacing pulses are delivered during the escape interval, then heart rhythm recovery is improved, but inappropriate therapy may occur if cardiac events are not accurately detected
Solution Approach 1:
The sensing threshold is pre-adjusted to higher levels immediately following electrical stimulation before cardiac signals return to normal amplitude. This preliminary adjustment prevents inappropriate pacing delivery during the critical early recovery phase when signals are still low-amplitude, ensuring therapy appropriateness without delaying recovery.
Solution Approach 2:
The system continuously monitors cardiac electrical signals and compares them against the dynamically adjusted threshold. When signals exceed the threshold, the escape interval is reset and pacing is appropriately withheld. This feedback mechanism ensures that pacing decisions are based on actual cardiac activity, preventing inappropriate therapy while maintaining timely recovery.
3Speed
If the escape interval timer is reset on every sensed event, then pacing control responsiveness is improved, but the timer may not continue running appropriately for low-amplitude signals post-shock
Solution Approach 1:
Different quality criteria are applied to sensed events depending on the timing relative to electrical stimulation. Immediately post-shock, only high-amplitude signals that clearly exceed the elevated threshold are considered valid for resetting the escape interval. As time progresses and the threshold decreases, the system becomes more responsive to lower-amplitude signals, achieving both responsiveness and accuracy at different stages.
Data Source
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AI summary
A medical device is configured to deliver a shock to a patient's heart via electrodes coupled to the medical device and set an escape interval timer to start running an escape interval after delivering the electrical shock. A sensing module of the medical device is configured to sense a cardiac event in response to a cardiac electrical signal received by the medical device crossing a sensing threshold. The medical device determines if the cardiac event meets reset criteria and allows the escape interval timer to continue running the escape interval if the cardiac event does not meet the reset criteria