Cardiac Signal Morphology Gating for Noisy VT Detection
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Solution Overview
Problem
Medical devices face challenges in accurately detecting cardiac electrical signals due to noise contamination, particularly when using extra-cardiovascular electrodes, which can lead to false detection of ventricular tachyarrhythmias.
Innovation Solution
A medical device system that includes a sensing circuit with multiple channels to detect R-waves and store time segments of cardiac electrical signals, determining morphology parameters to identify noisy segments and withholding tachyarrhythmia detection when a threshold number of noisy segments are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If extra-cardiovascular electrodes are used for sensing cardiac electrical signals, then the device can be implanted with fewer constraints and improved patient comfort, but the sensed signals become contaminated with noise leading to false detection of ventricular tachyarrhythmias
Solution Approach 1:
The patent segments the cardiac cycle into distinct phases (QRS complex, T-wave, ST-segment) and applies different noise detection algorithms to each segment. By dividing the signal analysis into morphologically-defined segments, the system can identify noise contamination more accurately without compromising the overall reliability of tachyarrhythmia detection in extra-cardiovascular leads.
Solution Approach 2:
The patent dynamically changes detection parameters based on signal morphology characteristics. When noise is detected in specific morphological segments, the system adjusts detection thresholds and criteria for that segment while maintaining normal detection in clean segments, thereby preserving reliability without sacrificing the ease of implantation benefit.
2Reliability
If noise detection algorithms are applied to cardiac electrical signals, then false detection of ventricular tachyarrhythmias is reduced, but the device complexity increases
Solution Approach 1:
The patent performs preliminary noise detection and signal quality assessment before final tachyarrhythmia detection. By pre-identifying noisy segments and flagging them for rejection, the system simplifies the main detection algorithm's workload, reducing overall device complexity while maintaining high detection accuracy through a two-stage processing approach.
Solution Approach 2:
The patent creates a simplified morphological template or reference model of expected cardiac signal patterns and compares incoming signals against this template. This copying approach allows noise detection without requiring complex real-time analysis, reducing device complexity while maintaining reliability through pattern matching.
Data Source
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AI summary
A medical device system, such as an extra-cardiovascular implantable cardioverter defibrillator ICD, senses R-waves from a first cardiac electrical signal by a first sensing channel and stores a time segment of a second cardiac electrical signal in response to each sensed R-wave. The medical device system determines a morphology parameter correlated to signal noise from time segments of the second cardiac electrical signal, detects a noisy signal segment based on the signal morphology parameter; and withholds detection of a tachyarrhythmia episode in response to detecting a threshold number of noisy signal segments.