Heart Sound Detection Windows for Diastolic Function
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Solution Overview
Problem
Current medical devices face challenges in reliably and accurately detecting third (S3) and fourth (S4) heart sounds, which are indicative of diastolic dysfunction and worsening heart failure, due to their weak signal intensity and susceptibility to interference from physical activity and cardiac electrostimulation.
Innovation Solution
A patient management system that includes a signal receiver to receive heart sound and impedance signals, using a heart sound detector circuit to determine detection windows for S3 and S4 based on impedance signals, and a heart failure detector circuit to generate a cardiac diastolic function indicator (DFI) for timely detection of worsening heart failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If heart sound sensors are used to detect S3 and S4 components, then diagnostic information about diastolic dysfunction is obtained, but detection reliability deteriorates due to weak signal intensity and interference
Solution Approach 1:
The patent segments the detection process into distinct phases by defining specific detection windows (S3 window and S4 window) within the cardiac cycle. The S3 detection window is positioned between S2 and the peak of the impedance signal, while the S4 detection window is positioned between the impedance peak and the next S1. This temporal segmentation allows the system to focus on specific time intervals where S3 and S4 are most likely to occur, improving detection reliability despite weak signal intensity.
Solution Approach 2:
The patent applies preliminary action by using the impedance signal to pre-define detection windows before attempting to detect heart sounds. The system first identifies the timing of S2 and the impedance peak, then uses these reference points to establish the S3 and S4 detection windows. This preliminary positioning of detection windows based on impedance characteristics enables more reliable subsequent detection of the weak S3 and S4 heart sound components.
2Reliability
If frequent patient monitoring is implemented, then heart failure hospitalization is reduced, but device battery life is shortened
Solution Approach 1:
The patent implements periodic action by monitoring heart sounds only during specifically defined detection windows (S3 window and S4 window) rather than continuously. The system activates the heart sound detector circuit only during these predetermined time intervals within each cardiac cycle, allowing the device to maintain effective monitoring while consuming less power during non-detection periods, thus extending battery life.
3Adaptability or versatility
If heart sound detection is performed during physical activity or electrostimulation, then comprehensive monitoring is achieved, but detection accuracy deteriorates due to signal interference
Solution Approach 1:
The patent uses the impedance signal as an intermediary to facilitate accurate heart sound detection during physical activity and electrostimulation. The impedance signal serves as a reference that helps identify the timing of cardiac events and defines the detection windows. By using impedance as an intermediary reference, the system can distinguish between genuine heart sounds and interference from physical activity or electrostimulation, maintaining detection accuracy under various conditions.
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 system enhances the detection of S3 and S4 heart sounds, improving the assessment of diastolic function and reducing healthcare costs by accurately identifying worsening heart failure events, thereby minimizing unnecessary medical interventions and extending device battery life.
Implementation Method 1
Heart sounds are associated with mechanical vibrations of the heart and the blood flow through the heart
Implementation Method 2
an impedance signal sensed from the patient
Data Source
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AI summary
Systems and methods for monitoring and treating patients with heart failure are described. A signal receiver may receive a heart sound (HS) signal and an impedance signal sensed from the patient. A heart sound detector circuit may use at least the received impedance signal to determine a HS detection window, and detect a HS component indicative of cardiac diastolic function from the received HS signal within the HS detection window. The system may include a heart failure detector circuit that may generate a cardiac diastolic function indicator (DFI) using the detected HS component and, in certain examples, may detect worsening heart failure using the generated DFI. The system may include a therapy circuit to deliver or adjust an electrostimulation therapy based on DFI.