Development of a wearable device for the acquisition of a six-derivations ECG for self-monitoring of cardiovascular diseases

Developed over a century ago, the electrocardiogram provides invaluable informa- tion about the state of health of the heart, aiding the diagnosis and management of various cardiovascular conditions. Cardiovascular diseases have significant impact on health, quality of life and eco- nomics, being the major cause of death and disability worldwide. In Europe, CVDs are the leading cause of death, accounting for 32% of all deceases, with an esti- mated cost of €210 billion annually. Addressing CVDs through monitoring and prevention is crucial to improve health expectancy and reduce the economic burden of these diseases. It is in this scenario that smart wearable devices fit. In fact, they let self-monitoring of heart rate and activity. These information, together with other vital parame- ters, provide feedback to cardiologists, allowing them to remotely monitor patients, eventually detecting early warning signs of CVDs, and to intervene with cures be- fore complications might occur. There are currently several devices that allow self monitoring of heart activity, but they are not designed to provide a comprehensive diagnosis of cardiac condi- tions. They commonly provide just numerical information about heart activity, and eventually report a single-lead ECG. The aim of this thesis is thus to study and to realise an innovative wearable device capable of overcoming these limitations acquiring a six-leads medical ECG in a non invasive way. While single-lead ECGs offer limited diagnostic utility as the electrical activity of the heart comes from one direction only, a six-leads ECG records information from six different electrodes placed on specific locations of the chest and of the limbs. This way, it allows diagnosis of cardiac conditions such as arrhythmia, ischaemia and heart blocks. The device conceived in this thesis project uses an ultra-compact design with just three electrodes, leveraging on the mathematical relationship between the six leads. Going into the details of the signal elaboration system. The device simultaneously acquires two differential signals from the input electrodes. Common mode noise is reduced using an instrumentation amplifier and different analog filters have been tested to reduce other sources of noise. Signals are ampli- fied and sampled with a high resolution 24-bit ADC. Acquired data are sent to a microcontroller and transmitted via Bluetooth to a smartphone application which displays acquisitions in real time. Furthermore, elaboration includes processing of the signals through digital Finite Impulse Response filters. Practically, the development of the thesis project has gone through the following steps: • Pen and paper design of the different functional blocks of the circuit. • Schematic diagram and PCB layout realization using Cadence OrCAD. • Firmware development. • Implementation of DSP filtering techniques. The combination of digital and analog filtering of the acquired signals made it possible to create a device capable of acquiring a high quality six-leads electrocar- diogram maintaining an extremely compact design. By offering an accessible and user-friendly solution, this device potentially simpli- fies and changes the current conception of ECG monitoring, improving prevention strategies, diagnosis, and treatments of cardiovascular diseases.