Far-Field EGM Ventricular Sensing to Reduce Oversensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Implantable medical devices (IMDs) face challenges in reliably detecting ventricular sensed events, particularly with far-field EGM signals, leading to oversensing issues that can result in inappropriate shocks and the need for device replacement.
Innovation Solution
A method and apparatus that utilize two dynamic sensing thresholds and refractory periods to detect positive and negative portions of non-rectified far-field EGM signals, rejecting double-counted events through shared refractory periods and adjusting thresholds based on signal peaks, enabling accurate arrhythmia detection and discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single dynamic sensing threshold is used to detect ventricular sensed events from far-field EGM signals, then the sensitivity for detecting low amplitude R-waves is improved, but the rate of oversensing (T-wave oversensing and R-wave double-counting) increases
Solution Approach 1:
The patent divides the sensing process into two separate channels: one for detecting positive deflections (R-waves) and another for detecting negative deflections (T-waves). By segmenting the single threshold into two opposing thresholds, the system can independently control sensitivity for each wave type, thereby improving R-wave detection while reducing T-wave oversensing.
Solution Approach 2:
The patent inverts the sensing approach by creating opposing sensing thresholds where one threshold detects positive deflections and the other detects negative deflections. This inversion allows the system to distinguish between R-waves (positive) and T-waves (negative) by their opposite polarities, eliminating the oversensing problem that occurs with a single non-directional threshold.
2Measurement precision
If signal rectification is applied to far-field EGM signals to enhance R-wave detection, then the amplitude of R-waves is increased, but R-wave double-counting occurs due to wide and complex morphology during VT and VF
Solution Approach 1:
The patent segments the rectified signal into positive and negative components, each processed through separate sensing thresholds. This segmentation prevents double-counting of wide R-waves during VT and VF by ensuring that only one polarity threshold is triggered per cardiac cycle, even when the morphology is complex and prolonged.
Solution Approach 2:
The patent applies different sensing characteristics to different portions of the signal by using separate positive and negative thresholds with potentially different sensitivity levels. This allows local optimization where the positive threshold is tuned for R-wave detection while the negative threshold is tuned to reject T-waves, addressing the specific quality issues of each wave type independently.
3Measurement precision
If the sensing threshold is lowered to detect low amplitude R-waves during fibrillation, then the detection sensitivity is improved, but T-waves and noise are mistakenly sensed as R-waves
Solution Approach 1:
The patent uses inverted sensing thresholds where the positive threshold detects R-waves and the negative threshold detects T-waves. By lowering only the positive threshold while maintaining an appropriate negative threshold, the system can detect low amplitude R-waves during fibrillation without mistakenly sensing T-waves, as the negative threshold acts as a protective barrier against T-wave oversensing.
Solution Approach 2:
The patent applies different threshold levels to different polarities of the signal. The positive threshold is lowered to enhance R-wave detection sensitivity, while the negative threshold is maintained at a higher level to reject T-waves and noise. This local quality adjustment allows asymmetric threshold optimization tailored to the specific characteristics of R-waves versus T-waves.
Data Source
AI summary
Described herein are methods, devices, and systems that identify ventricular sensed (VS) events from a signal indicative of cardiac electrical activity, such a far-field EGM or ECG signal, and monitor for an arrythmia and/or perform arrythmia discrimination based on the VS events. Beneficially, such embodiments reduce the probability of double-counting of R-wave, or more generally, of oversensing VS events, and thereby provide for improved arrythmia detection and arrythmia discrimination.