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Unobtrusive Estimation of Cardiac Contractility and Stroke Volume Changes Using Ballistocardiogram Measurements on a
Hazar Ashouri1, Lara Orlandic2, Omer T Inan3
1School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. hazarashouri@gatech.edu.
Insights
A novel ballistocardiogram (BCG) system using a high-bandwidth force plate accurately monitors heart failure patients' cardiovascular health. This non-invasive technology improves stroke volume and contractility measurements, enhancing patient care outside clinical settings.
Area of Science:
- Biomedical Engineering
- Cardiovascular Physiology
- Medical Technology
Background:
- Heart failure (HF) management requires continuous monitoring of cardiovascular health indicators like cardiac contractility and stroke volume (SV).
- Current methods for measuring these parameters are often invasive, expensive, or limited to clinical settings, hindering dynamic patient care.
- Unobtrusive, low-cost technologies are needed for remote patient monitoring to enable timely therapeutic adjustments.
Purpose of the Study:
- To evaluate the accuracy of a high-bandwidth force plate system for measuring cardiac contractility (via pre-ejection period, PEP) and stroke volume (SV) changes using ballistocardiogram (BCG) signals.
- To compare the performance of the force plate BCG system against a previously developed modified weighing scale BCG system.
- To assess the potential of this non-invasive technology for improving cardiovascular health monitoring in heart failure patients.
Main Methods:
- Subjects stood on a high-bandwidth force plate while holding electrodes for simultaneous electrocardiogram (ECG) detection to capture BCG and ECG signals.
- Cardiac contractility was assessed by measuring the pre-ejection period (PEP) from BCG-ECG signals.
- Stroke volume (SV) changes were estimated from the force plate BCG data.
- Accuracy was evaluated by comparing PEP and SV change estimations with established clinical methods and against a prior scale-based BCG system.
Main Results:
- The force plate BCG system demonstrated superior accuracy in PEP estimation compared to the scale BCG system (r² = 0.85 vs. r² = 0.81 at rest, and r² = 0.92 during recovery).
- The improved accuracy is attributed to the wider bandwidth of the force plate.
- Estimations of stroke volume (∆SV) changes using the force plate BCG system showed a low average error of 5.3% (±4.2% SD).
- Signal-to-noise ratio (SNR) was slightly better with the force plate, though motion artifacts remained a limiting factor.
Conclusions:
- A high-bandwidth force plate system enables accurate, non-invasive measurement of cardiac contractility and stroke volume changes via BCG.
- This technology offers a promising, inexpensive solution for continuous cardiovascular health monitoring in heart failure patients outside the clinic.
- The enhanced accuracy and potential for dynamic monitoring can significantly improve the continuity and effectiveness of heart failure care.
Abstract:
Unobtrusive and inexpensive technologies for monitoring the cardiovascular health of heart failure (HF) patients outside the clinic can potentially improve their continuity of care by enabling therapies to be adjusted dynamically based on the changing needs of the patients. Specifically, cardiac contractility and stroke volume (SV) are two key aspects of cardiovascular health that change significantly for HF patients as their condition worsens, yet these parameters are typically measured only in hospital/clinical settings, or with implantable sensors. In this work, we demonstrate accurate measurement of cardiac contractility (based on pre-ejection period, PEP, timings) and SV changes in subjects using ballistocardiogram (BCG) signals detected via a high bandwidth force plate. The measurement is unobtrusive, as it simply requires the subject to stand still on the force plate while holding electrodes in the hands for simultaneous electrocardiogram (ECG) detection. Specifically, we aimed to assess whether the high bandwidth force plate can provide accuracy beyond what is achieved using modified weighing scales we have developed in prior studies, based on timing intervals, as well as signal-to-noise ratio (SNR) estimates. Our results indicate that the force plate BCG measurement provides more accurate timing information and allows for better estimation of PEP than the scale BCG (r² = 0.85 vs. r² = 0.81) during resting conditions. This correlation is stronger during recovery after exercise due to more significant changes in PEP (r² = 0.92). The improvement in accuracy can be attributed to the wider bandwidth of the force plate. ∆SV (i.e., changes in stroke volume) estimations from the force plate BCG resulted in an average error percentage of 5.3% with a standard deviation of ±4.2% across all subjects. Finally, SNR calculations showed slightly better SNR in the force plate measurements among all subjects but the small difference confirmed that SNR is limited by motion artifacts rather than instrumentation.
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