IMD Disturbance Detection for False Cardiac Event Filtering
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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 exposure to electromagnetic interference (EMI), leading to undesirable abrupt changes in electrocardiogram (ECG) or electrogram (EGM) signals.
Innovation Solution
The IMD is equipped with sense and disturbance detection circuitry to detect non-biological disturbances by monitoring the slew rate and magnitude of differential signals between electrodes, distinguishing between biological and non-biological events using slew rate and amplitude thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are used to sense cardiac electrical activity continuously, then monitoring capability is improved, but false detections occur due to electrode contact loss or EMI
Solution Approach 1:
The disturbance detection circuitry proactively monitors the differential signal for signs of non-biological disturbances (such as electrode contact loss or EMI) before these can cause false cardiac event detections. By continuously analyzing signal characteristics like slew rate and magnitude, the system identifies disturbances in advance and prevents them from triggering incorrect arrhythmia detections
Solution Approach 2:
The disturbance detection circuitry acts as an intermediary between the sense circuitry and the cardiac event detection logic. It analyzes the differential signal independently and generates disturbance indications that can override or modify the interpretation of cardiac events, thereby filtering out false detections caused by electrode contact loss or electromagnetic interference
2Reliability
If disturbance detection circuitry is added to detect non-biological disturbances, then false detections are reduced, but device complexity increases
Solution Approach 1:
The disturbance detection circuitry is designed to perform multiple functions using the same hardware resources. It monitors signal magnitude, slew rate, and other characteristics to detect various types of non-biological disturbances (electrode contact loss, EMI, lead defects) with a single integrated circuit block, rather than requiring separate detection mechanisms for each disturbance type
Solution Approach 2:
The disturbance detection circuitry utilizes the existing differential signal from the sense circuitry without requiring additional external sensors or complex processing. It self-sufficiently analyzes the signal characteristics using simple comparison logic against predetermined thresholds, minimizing the need for additional system resources while achieving reliable disturbance detection
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 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 IMD (101, 501) includes a controller (120, 520) communicatively coupled to the sense circuitry (116, 544, 550) and the disturbance detection circuitry (210) and configured to detect based on the differential signal an episode of asystole, an episode sinus pause, a premature ventricular contraction, or premature atrial contraction, and classify, as a false positive, a detection of the episode of asystole, the episode sinus pause, the premature ventricular contraction, or the premature atrial contraction, when the non-biological disturbance detected by the disturbance detection circuitry (210) at least partially coincides with the detection of the episode of asystole, the episode sinus pause, the premature ventricular contraction, or the premature atrial contraction.