The Future of Cardiovascular Disease Management: Wearable Technology

Cardiovascular disease (CVD) refers to diseases of the heart and blood vessels, and includes conditions such as coronary heart disease (also known as ischaemic heart disease), cerebrovascular disease (stroke), heart failure, rheumatic heart disease and hypertension (high blood pressure).

CVD is the leading cause of death globally.  According to the World Health Organisation, deaths due to CVD are expected to double by the year 2030 and will continue to be the leading cause of death worldwide. Australia has seen a major decline in cardiovascular death rates since a alarmingly high levels in the late 1960's. Much of this decline is attributed to improved prevention, detection, and management over the past 60 years. Nevertheless, CVD remains the leading cause of death in Australia, with 45,600 deaths attributed to CVD in Australia in 2011. 

Advances being made in the Management of CVD?

Among all the deaths caused by CVD, about two-thirds of them happen in out-of-hospital settings. Acute cardiovascular events cause a large number of deaths without any prior symptoms or with subtle symptoms that fail to alert the necessary attention of patients.

The concept of monitoring an individual's cardiovascular function in the home and in community settings was first introduced more than 50 years ago, when Holter monitoring was proposed (in the late 1940s) and later adopted (in the 1960s) as a clinical tool. A Holter monitor is a battery-operated portable device most commonly used to detect and record the heart's electrical activity (electrocardiography or ECG).

The data are uploaded into a computer which then automatically analyzes the input, counting ECG complexes, calculating summary statistics such as average heart rate, and minimum and maximum heart rate. Holter monitors have wires that connect to small sensors (electrodes) attached to the patient's chest. Wires connect the sensors to a recording device called a monitor.

The monitor can be clipped to a belt or carried in a pocket. Given the rapid current advances in electronics and communication technologies, new unobtrusive medical devices are under development which can monitor various cardiovascular parameters such as ECG, heart rate, blood pressure, blood oxygen saturation, and even intracardiac pressures. These devices can be worn continuously by patients, and data can be remotely transmitted from the patient's location directly to a physician’s office computer.

Types of Wearable Technology Being Developed

Wearable electrocardiogram (ECG) devices

Imec ECG necklace (2010)

The ECG necklace monitors vital statistics and makes the data available to physicians through a mobile network. In case of an emergency, the health provider is automatically alerted and can take necessary actions. The Arise ECG Necklace integrates Imec’s proprietary ultra-low power readout chips enabling long-term autonomy (24/7 recording for one week) and technologies that reduce motion-induced artifacts and false alarms. Ambulatory cardiac monitoring systems today suffer from inaccurate measurements due to artifacts which are inherent to ambulatory situations. The embedded beat detection algorithm of the Imec ECG necklace has been optimised for robust heart beat detection. It copes with baseline wander, EMG (electromyogram) and motion artifacts, and high and variable electrode impedance.

Imec Health Patch

Holst Centre and Imec have unveiled a prototype flexible health patch weighing just 10g – half the weight of current products. The patch uses real-time electrocardiogram (ECG), tissue-contact impedance and accelerometer information to accurately monitor physical activity. Thanks to the advanced system in package (SiP) technology from Shinko Electric Industries Co., Ltd., the electronics module measures less than two by two centimeters. The high accuracy algorithms, low power consumption, and small size and weight make it ideal for consumer applications.

iRhythm Zio Patch

Housed in a thermoplastic elastomer, the device uses only a single lead, rather than the three typically employed by a conventional Holter. The Zio Patch is thus capable of providing only one view of a patient’s rhythm, rather than multiple views that can be helpful when diagnosing particularly complex arrhythmias. The device records 14 days of data.

Wearable Blood Pressure Monitors

High blood pressure is the leading modifiable risk factor for cardiovascular diseases, from heart attack to stroke. The value of continuous, real-time blood pressure measurements outweighs that of isolated screenings at the doctor's office or pharmacy. Wearable devices also represent an attractive alternative to the use of home sphygmomanometers which can be cumbersome and, to the extent that some skill is involved, can be inaccurate.

iHealth blood pressure monitor

The monitor connects to a user's mobile devices via Bluetooth, or to a personal computer via a USB cord, and is meant to be worn inside a vest. It offers round-the-clock monitoring without requiring that a user change anything about his or her lifestyle or routine. Users can choose how often it delivers blood pressure readings, with an option of 15-, 30-, 45-, 60-, or 120-minute intervals.

Wearable blood pressure patch

The device, developed by the team from Seoul National University and the Electronics and Telecommunications Research Institute in Daejeon, on the other hand, promises to provide continuous BP monitoring with minimal impact on the user's normal activities. This monitor calculates blood pressure by combining ECG with ballistocardiograph (BCG) data – a measure of the physical forces exerted through the body by the heart's contractions.

Devices have been developed for this method before, using multiple sensor types to gather the signals for ECG and BCG, increasing the complexity of the system and power consumption; both particular issues in wearable systems. Like other wearable health and fitness devices, the data is then sent in real time to a computer software program, where it is recorded and interpreted.

Healthstats blood pressure wrist watch

Hewlett-Packard and Healthstats International, a Singapore company, have joined efforts in developing a device, which has the size and look of a wrist watch, to continuously monitor blood pressure. 

The Healthstats device relies on a sensor that rests against an artery in the wrist and detects the shape of the pressure wave as blood flows through it.

One issue, as yet unanswered, is how accurate the device is at measuring blood pressure when the user is moving around.

Healthstats has shown that the monitor works as well as other measures when users are sitting still, but has yet to publish comparable results for patients in motion.

Empastrap blood pressure wrist watch

The company STBL Medical Research AG (STBL) has developed a device that can be worn comfortably on the wrist and records the blood pressure continuously -- with no pressure cuff or invasive procedure. The measurement is carried out by several sensors which simultaneously measure the contact pressure, pulse and blood flow on the surface of the skin in the vicinity of the wrist. Engineers had one particular obstacle to overcome in this new technology: the pressure of the device on the skin changes constantly, meaning that highly sensitive correctional measurements are necessary. Empa's Laboratory for High Performance Ceramics sought a suitable solution to this problem within the scope of a CTI project. A sensor made from piezo-resistive fibres in the wristband measures the contact pressure of the device on the skin. Changes in signal strength due to slippage or muscle tension could lead to incorrect measurements. It is these changes that the Empa sensor registers -- enabling the measurements to be corrected accordingly. The fibre is electrically conductive, detects any movement or change in pressure, converts this into an electrical signal and transmits this to the measuring device. This enables the measuring accuracy of the "blood pressure watch" to be increased by more than 70 per cent.

Wireless Pulse Oximeters

iHealth wireless pulse oximeter

This oximeter is a reliable way to spot-check blood oxygen saturation and pulse rate. This lightweight and portable device takes fast, noninvasive measurements at the fingertip. Primary uses are sports training and recreational activities.

Onyx II Model 9560 wireless fingertip pulse oximeter

From Nonin Medical, this Wireless oximetry allows clinicians to remotely monitor the oxygen saturation and heart rate of patients with chronic diseases such as congestive heart failure.

Ingestion Event Markers

Proteus Digital Health Ingestion Event Marker

FDA-approved Ingestion Event Markers are ingestible sensors that can be placed inside a pill and transmit information on when it was consumed, or provide metrics like heart rate, body position, and activity, to a patch on the user’s stomach. From that patch, the data can be sent to an app on the patient’s phone and then to a healthcare provider, who can use the information to adjust medications and treatments. With the patient’s consent, the information is accessible by caregivers and clinicians, helping individuals to develop and sustain healthy habits, families to make better health choices, and clinicians to provide more effective, data-driven care.

Intracardiac Pressure (Hemodynamic Monitoring)

Heart failure is a chronic progressive disorder affecting more than 5 million people in the United States and is responsible for more than 1 million hospitalisations each year.The Implantable Hemodynamic Monitor (IHM) System was developed to assist clinicians in managing the volume status in heart failure patients.

The Chronicle Implantable Hemodynamic Monitor (IHM) System

The Chronicle implantable hemodynamic monitor (Medtronic) is designed to continuously monitor intracardiac pressures, body temperature, physical activity, and heart rate in patients with advanced heart failure. The implanted device has a lead that travels into the heart through a vein. It provides continuous recordings of pressure, rate and function of the heart. In the most advanced version of the monitor, a patient can simply clip a memory device onto a home telephone to transmit data to a physician. Studies of the device have demonstrated that the Chronicle system is safe and potentially offers more objective means of assessing and adjusting therapy in heart failure patients. The constant monitoring holds promise as a way to better schedule the delivery of medication based on how the heart functions at different times of the day. How the heart rate responds during sleep can also be an indicator of disease progression in patients with congestive heart failure.

The Clinical Value of Wearable Devices

A great deal of progress has been achieved in the field of wearable sensors and systems within the past decade. Wearable devices are no longer just fitness bands and smartwatches. Wearable devices offer constant, objective monitoring of important physiologic parameters over extended periods of time. No longer limited by snapshot assessments of patients at isolated office visits, the clinician is better equipped to make appropriate, individualised treatment decisions. Wearable technology is a welcome addition to the future of cardiovascular disease management.

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