Bluetooth LE wearable ECG heart monitor detects cardiac rhythm disorders to identify risk of stroke

Nordic Semiconductor today announces that AppSens, a Lillesand, Norway-based medical technology manufacturer, has selected Nordic’s nRF52832 Bluetooth® Low Energy (Bluetooth LE) System-on-Chip (SoC) to provide the core processing power and wireless connectivity for its ‘ECG247 Smart Heart Sensor’. 

The ECG247 Smart Heart Sensor is a wearable electrocardiographic (ECG) heart monitor designed to detect atrial fibrillation and other cardiac arrhythmias. Atrial fibrillation is the most common cardiac rhythm disorder and is a common cause of stroke. ECG247 consists of a disposable electrode-patch to fasten the sensor to the patient’s chest and a reusable electronic component to achieve reliable electrical connection for the measurement of ECG signals. The solution can be used by patients to self-test their own heart health, including during exercise/activity, while also supporting remote patient monitoring and telehealth applications. Medical professionals can use the platform to screen people who are at increased risk of stroke due to heart rhythm disorders or who have symptoms of rhythm disorders such as palpitations or fast heart rate. 

Fully-automatic power management system

The ECG247 Smart Heart Sensor uses the nRF52832 SoC’s powerful 64MHz, 32-bit Arm® Cortex® M4 processor with floating point unit (FPU) to support the wearable’s integrated sensors and run proprietary algorithms for continuously measuring and analyzing the electrical activity in the patient’s heart for arrhythmia. The SoC’s processor, together with its generous memory allocation of 512kB Flash and 64kB RAM, supports the application’s complex floating point and digital signal processing computations. Moreover, the ultra-low power characteristics of the Nordic SoC—built on features like the 2.4GHz radio’s 5.5mA peak RX/TX currents and a fully-automatic power management system—enable the device’s CR2032 coin-cell battery mounted to the disposable plaster-patch, to support continuous heart rate monitoring for up to 14 days before replacement. 

Using the Nordic SoC-enabled Bluetooth LE connectivity, the ECG data is relayed to the user’s Bluetooth 4.0 (and later) smartphone, where from an iOS and Android companion app the patient can access their measurements and detected arrhythmia conditions. The heart rhythm recordings are automatically transferred to and stored on a secure Cloud-based server where an AI-driven algorithm analyzes the detected arrhythmia episodes and either confirms the episode or rejects it in cases of “artefact disturbances” (electrical interference in rhythm monitoring). Medical doctors and cardiologists can then easily access the recorded ECG signals and detected arrhythmia episodes of their patients to provide a quick diagnostic evaluation. 

Nordic’s nRF52832 multiprotocol SoC combines the Arm Cortex M4 processor, with a 2.4GHz multiprotocol radio (supporting Bluetooth 5.2, ANT™, and proprietary 2.4GHz RF protocol software) featuring -96dB RX sensitivity. The SoC is supplied with Nordic’s S132 SoftDevice, a Bluetooth 5-certifed RF software protocol stack for building advanced Bluetooth LE applications. The S132 SoftDevice features Central, Peripheral, Broadcaster and Observer Bluetooth LE roles, supports up to twenty connections, and enables concurrent role operation. Nordic’s unique software architecture includes a clear separation between the RF protocol software and the customer’s application code, simplifying development and ensuring the SoftDevice doesn’t get corrupted when developing, compiling, testing, and verifying the application code. 

High radio sensitivity

“We have worked closely with our technology partners Jetro and Kitron and together have developed a solution taking advantage of Nordic’s technology,” says Tord Ytterdahl, CEO of AppSens. “We selected Nordic’s nRF52832 for the ECG247 Smart Heart Sensor due to the extremely low power consumption, Arm CPU capability with FP processing, and high radio sensitivity – which are important benefits for a wearable solution where the electronic print-board is positioned just 6mm above the patient’s skin, as RF signals are typically difficult to transmit in systems mounted close to the human body.

“Nordic’s SoftDevices implement the Bluetooth LE protocol stack in an efficient way and leave enough CPU resources to the application code, enabling real-time data processing to be embedded in the product. In addition, Nordic’s excellent technical support, reference designs, and quick response times are all important factors for developers of embedded systems for wireless sensors or solutions.”

• About AppSens
• About nRF52832
• About Nordic Semiconductor