Elsevier

Journal of Cardiac Failure

Volume 26, Issue 11, November 2020, Pages 948-958
Journal of Cardiac Failure

Wearable Patch-Based Estimation of Oxygen Uptake and Assessment of Clinical Status during Cardiopulmonary Exercise Testing in Patients With Heart Failure

https://doi.org/10.1016/j.cardfail.2020.05.014Get rights and content

Abstract

Background

To estimate oxygen uptake (VO2) from cardiopulmonary exercise testing (CPX) using simultaneously recorded seismocardiogram (SCG) and electrocardiogram (ECG) signals captured with a small wearable patch. CPX is an important risk stratification tool for patients with heart failure (HF) owing to the prognostic value of the features derived from the gas exchange variables such as VO2. However, CPX requires specialized equipment, as well as trained professionals to conduct the study.

Methods and Results

We have conducted a total of 68 CPX tests on 59 patients with HF with reduced ejection fraction (31% women, mean age 55 ± 13 years, ejection fraction 0.27 ± 0.11, 79% stage C). The patients were fitted with a wearable sensing patch and underwent treadmill CPX. We divided the dataset into a training–testing set (n = 44) and a separate validation set (n = 24). We developed globalized (population) regression models to estimate VO2 from the SCG and ECG signals measured continuously with the patch. We further classified the patients as stage D or C using the SCG and ECG features to assess the ability to detect clinical state from the wearable patch measurements alone. We developed the regression and classification model with cross-validation on the training–testing set and validated the models on the validation set. The regression model to estimate VO2 from the wearable features yielded a moderate correlation (R2 of 0.64) with a root mean square error of 2.51 ± 1.12 mL · kg–1 · min–1 on the training–testing set, whereas R2 and root mean square error on the validation set were 0.76 and 2.28 ± 0.93 mL · kg–1 · min–1, respectively. Furthermore, the classification of clinical state yielded accuracy, sensitivity, specificity, and an area under the receiver operating characteristic curve values of 0.84, 0.91, 0.64, and 0.74, respectively, for the training–testing set, and 0.83, 0.86, 0.67, and 0.92, respectively, for the validation set.

Conclusions

Wearable SCG and ECG can assess CPX VO2 and thereby classify clinical status for patients with HF. These methods may provide value in the risk stratification of patients with HF by tracking cardiopulmonary parameters and clinical status outside of specialized settings, potentially allowing for more frequent assessments to be performed during longitudinal monitoring and treatment.

Section snippets

Experimental Protocol

The study was conducted under a protocol reviewed and approved by the University of California, San Francisco, and the Georgia Institute of Technology Institutional Review Boards. All patients provided written consent before the procedure. We have conducted a total of 68 CPX tests in 59 patients with HFrEF (with 9 patients having 2 CPX tests separated by 253 ± 117 days). All of the patients were recruited from the cardiopulmonary stress test laboratory at the University of California, San

Results

Patient demographics and clinical characteristics are detailed in Table 1 and CPX characteristics are provided in Table 2. A survival analysis using subsequent events (left ventricular assisted device implantation, heart transplant, or cardiovascular death) occurring over 6 months after the initial collection of data is provided in the Supplementary Materials.

Discussion

With this proof-of-concept study, we have shown the potential of a small, lightweight, wearable patch capable of measuring SCG and ECG to estimate beat-by-beat VO2 estimation throughout a standard CPX procedure. Our results have shown that features from the wearable patch may capture the changes in cardiopulmonary demand during exercise and may be used to differentiate between stage C and stage D HFrEF. These promising initial results provide a foundation for determining cardiopulmonary

Conclusions

We have demonstrated that a wearable chest patch-based sensor capable of recording ECG and SCG may be used to estimate VO2 from CPX for patients with HF using a global regression model and may facilitate determination of clinical state of the patient. We thus demonstrated that wearable sensors can potentially be used to monitor cardiopulmonary health and to stratify disease risk for patients with HF. The approach described in this work may thus provide the capability to perform longitudinal CPX

Clinical Perspectives

Wearable technologies have the potential to allow monitoring of patients with HF in the ambulatory setting. In this work, we have shown that a wearable patch can estimate oxygen consumption during cardiopulmonary stress testing and can assist in the stratification of patients with HF based on the severity of their disease. Future work will investigate tracking physiologic changes and responses to interventions during daily activities at home in this patient population.

Financial Support

Supported in part by the National Heart, Lung and Blood Institute under R01HL130619. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Disclosures

O. T. Inan is a Scientific Advisor for Physiowave, Inc.

Acknowledgments

Dr Klein would like to acknowledge the research support from gifts from Joyce and Roger Isaacs and George Doubleday.

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