Cardiac Signal Template Segmentation for Posture-Dependent Rhythm Discrimination
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Solution Overview
Problem
Existing implantable medical devices (IMDs) face challenges in accurately discriminating between treatable heart rhythms, such as ventricular tachycardia (VT), which require therapy, and non-treatable rhythms, such as supraventricular tachycardia (SVT), due to changes in cardiac signal morphology induced by patient posture, often leading to inappropriate therapy delivery.
Innovation Solution
The IMD generates and stores cardiac electrical signal templates for multiple patient postures without requiring a posture sensor, allowing it to classify unknown rhythms as VT or SVT by comparing the morphology of sensed signals to stored templates across various sensing vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the IMD uses a single cardiac signal template for rhythm discrimination, then the device complexity is reduced, but the measurement precision deteriorates due to posture-induced signal morphology changes
Solution Approach 1:
The patent segments the single cardiac signal template into multiple posture-specific templates (supine, sitting, standing, left lateral, right lateral). Each template captures the characteristic morphology of cardiac signals in that specific posture, allowing accurate rhythm discrimination regardless of patient position. This segmentation resolves the contradiction by maintaining low device complexity through a systematic template organization while achieving high measurement precision through posture-appropriate template selection.
Solution Approach 2:
The patent performs preliminary action by pre-acquiring and storing multiple cardiac signal templates during different postures before actual rhythm discrimination is needed. These templates are stored in memory and automatically selected based on detected posture, eliminating the need for real-time template adaptation and ensuring accurate comparison even when posture changes occur during tachycardia episodes.
2Measurement precision
If the IMD acquires and stores multiple cardiac signal templates for different postures, then the measurement precision is improved, but the use of energy increases due to additional processing and storage requirements
Solution Approach 1:
The patent performs template acquisition and storage during periods when the patient is in stable postures (preliminary action), rather than continuously during all activities. This allows the system to build its template library during low-activity periods when energy consumption can be minimized, while still providing accurate rhythm discrimination when needed.
Solution Approach 2:
The system uses the patient's own cardiac signals during normal activity to automatically generate and update posture-specific templates without requiring external intervention or additional power-intensive processing. The device self-adapts to the patient's unique cardiac morphology in each posture, reducing the need for external programming and follow-up adjustments.
3Device complexity
If the IMD does not use a posture sensor to detect patient position, then the device complexity is reduced, but the reliability of rhythm discrimination deteriorates due to inability to select appropriate templates
Solution Approach 1:
The patent implements feedback by continuously monitoring cardiac signal characteristics and comparing them against the library of posture-specific templates. The system automatically identifies which template best matches the current signal morphology and uses that template for rhythm discrimination, creating a closed-loop system that adapts to posture changes without requiring direct posture sensing. This feedback mechanism maintains high reliability while avoiding the complexity of additional sensors.
Solution Approach 2:
The system performs self-position identification by analyzing the intrinsic characteristics of the cardiac signals themselves. Different postures produce distinct signal morphology patterns that the system automatically recognizes and uses to select the appropriate template, eliminating the need for external posture sensing while maintaining accurate rhythm classification.
Data Source
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AI summary
An implantable medical device system includes an implantable cardioverter defibrillator (ICD) for detecting and treating ventricular tachycardia (VT). The ICD includes a sensing module for sensing a cardiac signal from selected cardiac signal sensing vectors. A control module generates morphology templates of the cardiac signals for multiple patient postures for each of the available sensing vectors. A cardiac signal received during an unknown cardiac rhythm is compared to the morphology templates without determining a current posture of the patient. The unknown cardiac rhythm is detected and classified as supraventricular tachycardia in response to the cardiac signal matching at least one of the morphology templates.