IMD Disturbance Detection for Electrode Loss and EMI
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Solution Overview
Problem
Implantable medical devices (IMDs) experience false detections of cardiac events due to electrodes losing contact with tissue or becoming defective, leading to abrupt changes in sensed signals, which are not addressed by existing detection methods.
Innovation Solution
The IMDs incorporate sense circuitry to detect differential signals between electrodes, utilizing slew rate and amplitude thresholds to distinguish between biological and non-biological disturbances, such as electrode contact loss or electromagnetic interference, by monitoring the slew rate and duration of signal saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are used to sense ECG/EGM signals continuously, then cardiac electrical activity can be monitored, but false detections occur when electrodes lose contact with tissue or are exposed to EMI/MRI
Solution Approach 1:
The patent applies preliminary action by continuously monitoring the slew rate of differential ECG/EGM signals to detect non-biological disturbances before they cause false cardiac event detections. The disturbance detection circuitry is set up in advance with predetermined thresholds to identify when electrodes are losing contact or when EMI is present, allowing the system to preemptively flag or ignore subsequent false cardiac event signals.
Solution Approach 2:
The patent implements feedback by using the slew rate information from the differential signal to continuously adjust the interpretation of cardiac event detections. When the slew rate exceeds the predetermined threshold, the system provides feedback that this is a non-biological disturbance, which then modifies how subsequent signals are evaluated for cardiac events, preventing false positives.
2Reliability
If disturbance detection circuitry is added to monitor slew rate, then false detections are reduced, but device complexity increases
Solution Approach 1:
The patent applies merging by integrating the disturbance detection circuitry with the existing sense circuitry of the IMD. The disturbance detection functionality is combined with the cardiac signal sensing operations, allowing both functions to share hardware resources and processing pathways, thereby minimizing the increase in overall device complexity while still providing comprehensive disturbance detection.
Solution Approach 2:
The patent implements universality by designing the disturbance detection circuitry to serve multiple purposes: it monitors for electrode disconnection, detects EMI exposure, and identifies MRI exposure conditions all through a single slew rate monitoring mechanism. This multi-functional approach allows one circuit to handle various types of non-biological disturbances without requiring separate detection systems for each condition.
Data Source
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AI summary
An implantable medical device (IMD) (101, 501) is described herein. The IMD (101, 501) includes sense circuitry (116, 544, 550) configured to produce a differential signal (e.g., an ECG or EGM signal) indicative of a voltage potential difference between first and second electrodes (112, 114). The IMD (101, 501) additionally includes disturbance detection circuitry (210) configured to detect a non-biological disturbance based at least in part on a slew rate of the differential signal exceeding a slew rate threshold. The non-biological disturbance can be, e.g., at least one of the first or the second electrodes (112, 114) losing contact with the tissue of the patient within which the IMD (101, 501) is implanted, exposure of the IMD (101, 501) to EMI, or exposure of the IMD (101, 501) to a time-varying gradient magnetic field from an MRI system.