Implantable Device Adaptive Sense Threshold for Cardiac Detection
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Solution Overview
Problem
Implantable medical devices face challenges in reliably detecting cardiac events with varying signal amplitudes, leading to undersensing of cardiac events and false detection of bradycardia and asystole, particularly with small or large amplitude cardiac ectopies.
Innovation Solution
The processor device adaptively controls the sense threshold, keeping it constant after a peak detection and reducing it over time to ensure detection of low amplitude events, using a reference threshold derived from previous peak values to prevent false negatives and false positives, and employing a detection hold-off period to avoid immediate re-detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed sense threshold is used for detecting cardiac events, then the device operation is simple and energy-efficient, but cardiac events with small amplitudes are undersensed leading to false detection of bradycardia and asystole
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed sense threshold to a dynamic, time-varying sense threshold that automatically adapts to different signal conditions. The threshold is reduced over time according to a predetermined schedule, allowing the system to detect both large and small amplitude cardiac events without requiring complex real-time analysis or additional sensors.
Solution Approach 2:
The patent changes the parameter of the sense threshold over time according to a predetermined reduction schedule. The threshold starts at an initial value and is progressively reduced to minimum value over specified time periods, enabling the system to adapt to varying signal amplitudes without increasing device complexity or requiring additional hardware.
2Reliability
If the sense threshold is continuously reduced to detect small amplitude events, then detection sensitivity improves, but cardiac events occurring shortly after previous events are missed due to threshold being too high
Solution Approach 1:
The patent segments the threshold reduction process into distinct time periods with different reduction schedules. By dividing the detection timeline into segments (first time period, second time period, etc.), the system can apply different threshold strategies to different temporal contexts, ensuring both early event detection and sensitivity to subsequent events.
Solution Approach 2:
The patent implements periodic action through cyclic threshold reduction and maintenance phases. The threshold is reduced during certain time periods and held constant during others, creating a periodic pattern that balances between detecting early events and maintaining sensitivity to subsequent events. This cyclic approach ensures neither detection sensitivity nor timing is compromised.
Data Source
AI summary
An implantable medical device comprises a sensor device for obtaining a signal indicative of cardiac activity within a patient, and a processor device configured to process said signal obtained using the sensor device. The processor device is configured to detect a peak indicative of a cardiac event in said signal by comparing said signal to a sense threshold. The processor device in addition is configured to adaptively control said sense threshold such that the sense threshold in at least one time period assumes a value which is constant over said at least one time period, wherein the sense threshold is reduced after lapse of said at least one time period.