Wearable Defibrillator NSVT Detection via QRS Morphology
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Solution Overview
Problem
Existing cardiac monitoring systems, such as Wearable Cardioverter Defibrillators (WCDs), face challenges in accurately detecting and storing episodes of nonsustained ventricular tachycardia (NSVT) due to artifacts from patient motion and environmental noise.
Innovation Solution
The method involves processing electrocardiogram (ECG) signals to diagnose NSVT episodes by satisfying specific criteria such as NSVT time duration, QRS morphology similarity, heart rate threshold, and R-R stability, and storing these episodes for clinical review.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If WCD systems continuously monitor ECG signals to detect NSVT episodes, then detection capability is improved, but false positives from motion artifacts and environmental noise increase
Solution Approach 1:
The patent segments the ECG signal analysis into multiple independent criteria: NSVT time duration criterion (5-15 seconds), QRS morphology criterion (similarity to template), heart rate criterion (>150 BPM), and R-R stability criterion. Each criterion independently evaluates a specific aspect of the signal, and only when all criteria are satisfied is an NSVT episode confirmed. This segmentation allows the system to filter out motion artifacts and noise that would fail one or more criteria, thereby reducing false positives while maintaining detection sensitivity.
2Reliability
If the system uses multiple detection criteria to reduce false positives, then reliability is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary actions by continuously pre-processing ECG signals to generate and update a QRS template in advance. The template is created from normal sinus rhythm QRS complexes and stored for later comparison. This preliminary preparation allows the morphology criterion to quickly compare incoming QRS complexes against the pre-established template without complex real-time analysis, reducing computational complexity while maintaining high detection reliability.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the NSVT time duration threshold based on clinical guidelines (5-15 seconds) and using configurable criteria weights. The system can adapt the detection parameters such as heart rate threshold (>150 BPM) and R-R stability margin to balance sensitivity and specificity. This flexibility allows the system to maintain high reliability across different patient populations and clinical scenarios without requiring complex adaptive algorithms.
Data Source
AI summary
A method to monitor a patient's heart health is described. The method may include processing at least one electrocardiogram (ECG) signal and diagnosing an episode of nonsustained ventricular tachycardia (NSVT) based at least in part on the processing of the at least one ECG signal. In some embodiments, the NSVT episode may satisfy an NSVT time duration and a QRS criterion. The NSVT time duration may be between 5 seconds and 15 seconds. In some instances, the QRS criterion may be a temporary QRS template of two sequential incoming QRS complexes. In some embodiments, the method may determine a similarity between the temporary QRS template and at least two subsequent QRS complexes by calculating a feature correlation coefficient between the QRS template and the subsequent QRS complexes.