Development of a wearable belt with integrated sensors for measuring multiple physiological parameters related to heart failure

Cardiovascular diseases (CVDs) are a group of diseases of the heart and blood vessels, such as myocardial infarction, commonly known as heart attack, heart failure, rheumatic heart disease, and pulmonary artery disease.1.2πŸ‡§πŸ‡· According to the World Health Organization (WHO), CVDs are the leading cause of death, with an estimated 17.9 million deaths worldwide.1πŸ‡§πŸ‡· Heart failure (HF) is a critical CVD with an estimated 64.34 million cases worldwide3πŸ‡§πŸ‡· Heart failure is a progressive clinical syndrome characterized by a structural abnormality of the heart, in which the heart is unable to pump enough blood to meet the body’s needs. Due to this lack of blood supply, fluid accumulates in the lungs, which prevents oxygenation.4,5,6πŸ‡§πŸ‡· There are two types of HF: systolic HF with reduced ejection fraction (HFrEF) and diastolic HF with preserved ejection failure (HFpEF). Common causes of HFFER include cardiomyopathy, heart muscle disease, untreated high blood pressure, defective heart valves, and coronary artery disease. A common cause of HFPEF is left ventricular hypertrophy (LVH), a condition in which the left ventricle of the heart is thickened and the chamber is unable to sufficiently fill adequate cardiac output.7,8,9πŸ‡§πŸ‡· According to the Centers for Disease Control and Prevention (CDC), in 2018 there were 379,800 deaths, and 13.4% of the total mortality in the US was due to HFtwoπŸ‡§πŸ‡· Additionally, according to the American Heart Association, there are currently 6.2 million adults diagnosed with HF in the US, and that number is projected to increase to 8 million by 203010πŸ‡§πŸ‡· Current treatment for HF includes guideline-driven medications and surgically implanted devices, which can be very expensive. According to the CDC, an average of $30.7 billion was spent on treating HF in the US in 2012twoπŸ‡§πŸ‡· This financial burden is due to the downward trajectory of HF which, in later stages, leads to repeated hospitalizations. Due to this misdiagnosis, 17-45% of deaths occur within a year of initial hospitalization and 45-60% of deaths occur within five years.11πŸ‡§πŸ‡·

Continuous, real-time monitoring of HF symptoms can alert patients and providers of patient decompensation. The provider can then intervene with medication to prevent the patient from being hospitalized. Accumulation of fluid in the lungs is reflected by a decrease in thoracic impedance. Common symptoms of HF are related to fluid overload and include fatigue, weight gain and shortness of breath.7.8πŸ‡§πŸ‡· These symptoms can be monitored for HF progression. There are currently two implantable devices to monitor HF symptoms: an implantable cardioverter-defibrillator (ICD) and the CardioMEMSβ„’ Pulmonary Artery Monitor.8, 12, 13, 14πŸ‡§πŸ‡·

An ICD is recommended for patients with HFrEF as they are more likely to have lethal cardiac arrhythmias. An ICD also measures thoracic impedance and can alert providers to decreasing thoracic impedance, indicating more fluid in the lungs.15πŸ‡§πŸ‡· It is surgically implanted under the skin and detects lethal arrhythmias and restores normal heart rhythm with an electric shock. ICDs have an additional function as a pacemaker to speed up a very slow heart16πŸ‡§πŸ‡· An ICD requires an invasive surgical procedure for initial implantation and whenever the battery needs replacing, typically within 3 to 7 years17πŸ‡§πŸ‡· There are risks with any surgery and the procedure is also expensive. According to the ICD registry, the surgical replacement costs approximately $37,00018πŸ‡§πŸ‡· Additionally, electromagnetic fields can disrupt ICD performance, and the risk increases with increasing proximity.19, 20, 21, 22, 23πŸ‡§πŸ‡· It is important to note that ICDs are only recommended for patients with HFrEF; monitoring devices are not available for 50% of patients with HFPEF24πŸ‡§πŸ‡·

CardioMEMSβ„’ is a commercially available diagnostic tool for HF that can alert providers to increased pressure in the lungs. It is a small device (15 mm Γ— 3.5 mm Γ— 2 mm) that is implanted in the pulmonary artery and monitors changes in pulmonary artery pressure. Increased pulmonary artery pressure is an early indicator of worsening HF 25, 26, 27πŸ‡§πŸ‡· It’s expensive, approximately $17,75011, and not without risk. CardioMEMSβ„’ was approved by the Food and Drug Administration in 2014 for both HFrEF and HFpEF, and in its first three years, 5,500 devices were implanted in single patients. However, CardioMEMSβ„’ failed to predict 22 deaths out of 5,500 implants, 4 of which were due to HF28.29πŸ‡§πŸ‡· Additionally, sensor failure occurred in 46 cases, of which 13 required recalibration, 11 patients were hospitalized, and 14 sensors were discarded.28πŸ‡§πŸ‡·

Both currently available HF monitoring systems are not only expensive, but also pose significant safety concerns. Furthermore, the risks of invasive procedures cannot be ignored. Approximately half of patients with HF do not need an ICD and do not qualify for the chest monitoring it provides. Therefore, there is a critical need for non-invasive solutions for continuous, real-time monitoring of HF progression. Healthcare Wearable Devices (HWDs) can fulfill this need as HWDs are not only cost-effective but also safe and convenient for the user. In addition, they have proven to be a suitable solution for continuous and real-time monitoring of various biomarkers.30.31πŸ‡§πŸ‡· In addition to ICD and CardioMEMS, Sensible Medical’s Remote Dielectric Sensor (ReDS) also measures lung fluid content, but it is also not portable and cannot be used for care at all times.32πŸ‡§πŸ‡·

Furthermore, the VitalPatch by VitalConnect is a portable wearable device that can be used to monitor different vital signs related to cardiovascular disease.33πŸ‡§πŸ‡· These parameters include heart rate, heart rate variability, respiratory rate, body temperature, ECG, posture, and activity drop detection. However, it does not measure thoracic impedance, an important parameter for HF monitoring33πŸ‡§πŸ‡·

In this article, we present an HWD that has the potential to monitor important physiological parameters for patients with HF. These parameters include thoracic impedance, electrocardiogram (ECG), heart rate, and movement activity detection.

Thoracic impedance is a critical bio-signal for monitoring HF progression, having a magnitude between 60 and 1000 ohms, depending on the subject under consideration and the number of electrodes used to measure thoracic impedance.34πŸ‡§πŸ‡· As discussed, at the beginning of HF, fluid begins to accumulate in the thoracic region, this fluid retention decreases the impedance in this area. Yu et al. in their study with 33 patients with HF, they observed that before the onset of HF, thoracic impedance begins to decrease35πŸ‡§πŸ‡· Therefore, this decrease in thoracic impedance is a vital consideration for HF progression.36, 37, 38πŸ‡§πŸ‡· Thoracic impedance is assessed by placing electrodes in the thoracic region and measuring the resistance to ion flow in that area. When the heart is not pumping efficiently, fluid fills the chest cavity and facilitates the flow of ions, as fluid is more conductive than air. 35, 39, 40πŸ‡§πŸ‡· Increased load flow indicates a decrease in thoracic impedance. Likewise, with the absence of fluid within the thoracic region, loads face greater resistance to flow from one electrode to another, which indicates an increase in thoracic impedance.41πŸ‡§πŸ‡·

Likewise, the ECG is a vital biosignal for the diagnosis and prognosis of cardiovascular diseases. It is a representation of the flow of electrical signals through the heart.42πŸ‡§πŸ‡· As discussed, one of the symptoms of heart failure is abnormal heart rhythms known as cardiac arrhythmias.43πŸ‡§πŸ‡· Cardiac arrhythmia is an improper heartbeat in which the ECG is irregular and indistinguishable from regular sinus rhythm43πŸ‡§πŸ‡· These cardiac arrhythmias can be identified using ECG. Traditionally, in the outpatient setting, the ECG is measured using a Holter monitor that is not suitable for point-of-care (POC) use. In addition, cardiomyopathy causes decreased ejection fraction, in which the percentage of blood pumped with each heartbeat decreases.44πŸ‡§πŸ‡· To compensate for the loss of blood supply, the heart may beat at a higher rate than normal (60 to 100 beats per minute). This may not be enough to provide the body with the necessary cardiac output and lead to HF symptoms.

Fatigue is another symptom of IC, along with leg swelling or edema.7.8πŸ‡§πŸ‡· O’Donnell et al. performed a study of 13 patients with HF and found that patients with severe HF were less able to perform physical activity and therefore had low activity45πŸ‡§πŸ‡· Also, discomfort due to heart failure affects sleep patterns46.47πŸ‡§πŸ‡· These symptoms can be monitored using position sensors that can be used for better heart failure management.

This article will highlight the materials and methods involved in the development of the HWD for the acquisition of the above mentioned parameters along with their preliminary results. Furthermore, it will also discuss the challenges and future directions for using the discussed HWD for IC prediction.

Development of a wearable belt with integrated sensors for measuring multiple physiological parameters related to heart failure

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