Wearable cardioverter defibrillator (WCD) system computing heart rate from noisy ECG signal
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Solution Overview
Problem
The challenge in wearable cardioverter defibrillator (WCD) systems is that ECG signals are often corrupted by electrical noise, making it difficult to accurately interpret and deliver timely shocks to patients at risk of sudden cardiac arrest.
Innovation Solution
The WCD system employs electrodes to sense ECG signals, processes to detect sequential peaks, measure time intervals, and identify a representative duration that best meets a plausibility criterion, allowing for accurate heart rate computation and shock delivery despite noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If external electrodes are used to sense ECG signals in WCD systems, then the system can be worn externally without surgical implantation, but the ECG signals become corrupted by electrical noise making interpretation difficult
Solution Approach 1:
The patent introduces an intermediary signal processing system that mediates between the noisy external electrode signals and the final arrhythmia detection. The processor acts as a mediator that separates the useful ECG information from the electrical noise through advanced algorithms, allowing external electrodes to be used while maintaining detection accuracy.
Solution Approach 2:
The patent replaces the mechanical/physical approach of using implanted electrodes with an electronic/software-based solution. Instead of relying on the physical proximity and stability of implanted electrodes, the system uses digital signal processing, filtering algorithms, and noise cancellation techniques to achieve reliable ECG interpretation from external electrodes.
2Productivity
If traditional peak detection methods are used on noisy ECG signals, then the processing is simple and fast, but the heart rate computation becomes inaccurate
Solution Approach 1:
The patent applies preliminary signal conditioning and preprocessing actions before peak detection. The system performs filtering, noise reduction, and signal enhancement operations in advance, which prepares the noisy ECG signal for more accurate peak detection without significantly increasing processing time during critical arrhythmia detection.
Solution Approach 2:
The patent implements feedback mechanisms where the detected peaks and computed heart rate are continuously monitored and used to adjust the signal processing parameters. This feedback loop allows the system to refine its peak detection accuracy while maintaining fast processing speeds by adapting to the specific characteristics of the incoming signal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the WCD system to accurately compute heart rates and deliver shocks when necessary, even in the presence of noise, thereby improving patient safety and response time to arrhythmias.
Implementation Method 1
The WCD system further includes electronic components, such as a defibrillator and electrodes, coupled to the harness, vest, or other garment. When the patient wears the WCD system, the external electrodes may then make good electrical contact with the patient's skin, and therefore can help sense the patient's ECG.
Data Source
AI summary
In embodiments, a WCD system includes electrodes with which it senses an ECG signal of the patient. A processor may detect sequential peaks within the ECG signal, measure durations of time intervals between the peaks, including between non-sequential peaks, and identify a representative duration that best meets a plausibility criterion. The plausibility criterion may be that the representative duration is the one that occurs the most often, i.e. is the mode. Then a heart rate can be computed from a duration indicated by the representative duration and, if the heart rate meets a shock condition, the WCD system may deliver a shock to the patient. An advantage can be that the representative duration can be close to a good R-R interval measurement of a patient, notwithstanding noise in the ECG signal that is in the shape of peaks.