Cardiac Capture Verification Using Weighted Signal Analysis
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Solution Overview
Problem
Current heart stimulating devices face challenges in accurately distinguishing capture from loss of capture due to electrode polarization and limitations in detecting evoked responses, particularly in varying energy levels of stimulation pulses.
Innovation Solution
A method involving a control circuit and separate sensing electrode to deliver and sense pacing pulses, categorize signals, and determine a weight vector for calculating weighted areas within a time window to differentiate captured and non-captured signals, optimizing the capture verification condition for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same electrode is used for both emitting stimulation pulses and sensing evoked responses, then device complexity is reduced, but electrode polarization creates residual voltage that makes detection difficult
Solution Approach 1:
The patent divides the electrode system into separate pacing and sensing electrodes. The pacing electrode delivers stimulation pulses while the sensing electrode detects evoked responses, eliminating the polarization interference that occurs when the same electrode performs both functions.
Solution Approach 2:
The patent introduces a separate sensing electrode as an intermediary element between the pacing electrode and the detection circuitry. This intermediary electrode captures the evoked response signal without being subjected to the polarization effects of the pacing electrode.
2Reliability
If stimulation pulse energy is increased to ensure capture, then capture reliability is improved, but battery consumption increases
Solution Approach 1:
The patent implements a feedback mechanism where the sensing electrode detects evoked responses and provides information back to the control circuit. Based on this feedback, the system determines whether capture occurred and adjusts the stimulation pulse energy accordingly, delivering higher energy only when necessary to ensure capture.
Solution Approach 2:
The patent dynamically changes the energy parameter of stimulation pulses based on detected evoked responses. The system starts with lower energy pulses and increases energy only when capture is not detected, optimizing the balance between capture reliability and battery consumption.
3Device complexity
If simple amplitude-based detection is used for capture verification, then device complexity is reduced, but accuracy in distinguishing capture from loss of capture deteriorates
Solution Approach 1:
The patent extends the detection approach from simple amplitude measurement to multi-dimensional signal analysis. The control circuit analyzes multiple characteristics of the evoked response signal including amplitude, duration, morphology, and temporal features, thereby improving detection accuracy without significantly increasing device complexity.
Data Source
AI summary
In a cardiac stimulation method, device and system, a capture verification condition is determined. For this purpose, a number of pacing pulses are delivered to a heart chamber and signals are sensed within a time window following each pacing pulse. The sensed signals are stored and categorized as representing capture or non-capture. Using the stored signals, a weight vector is determined, that assigns different weights for different parts of each sensed signal within the time window. The weight vector is used for calculating a weighted area within the time window. The capture verification condition is determined by identifying whether the weighted area, calculated with the weight vector, of a sensed signal within the time window is above or below a predetermined value.