Multi-threshold Cardiac Sensing for Implantable Devices
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Solution Overview
Problem
Existing medical devices struggle to accurately sense cardiac electrical signals, particularly R-waves, while avoiding oversensing of T-waves and P-waves, which can lead to false detection of abnormal rhythms and unnecessary therapeutic interventions.
Innovation Solution
Implementing a multi-level cardiac event sensing threshold controlled by a sensing circuit, adjusted between threshold value levels at determined time intervals, using extra-cardiovascular electrodes to differentiate R-waves from T-waves and P-waves, thereby enhancing the sensitivity for detecting ventricular depolarizations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single cardiac event sensing threshold is used, then the device can detect abnormal rhythms with high sensitivity, but it causes oversensing of T-waves and P-waves leading to false detection
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the sensing threshold between at least two different threshold value levels at determined time intervals. The threshold is set to a first value during a first time interval and changed to a second value during a second time interval, allowing the device to adapt to different cardiac cycle phases and avoid oversensing T-waves and P-waves while maintaining sensitivity for detecting abnormal rhythms.
2Measurement precision
If the sensing threshold is lowered to detect low-amplitude R-waves, then sensitivity for detecting ventricular depolarizations increases, but oversensing of T-waves and P-waves increases
Solution Approach 1:
The patent implements dynamics by making the sensing threshold time-variable rather than fixed. The threshold dynamically changes between at least two different threshold value levels at determined time intervals, allowing the system to use lower thresholds during periods when T-waves and P-waves are less likely to occur, thereby maintaining high sensitivity for R-wave detection while reducing oversensing of other cardiac waves.
Data Source
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Figure 2A
AI summary
An implantable medical device system is configured to sense cardiac events in response to a cardiac electrical signal crossing a cardiac event sensing threshold. A control circuit is configured to determine a drop time interval based on a heart rate and control a sensing circuit to hold the cardiac event sensing threshold at a threshold value during the drop time interval.