Design and implementation of an ECG front end circuit /

Robaei, Mohammadreza
Since the first electrocardiogram (ECG) was recorded by Eindhoven in 1903, examination of the electrical activity of the heart using surface electrodes obtained great clinical significance over the years. According to annual report of World Health Organization in 2013, cardiovascular diseases are counted as one of the four major reasons of 80% of deaths in the world. Therefore, the ability to acquire high quality recordings of electrical activity of the heart from surface of the body would be highly beneficial for diagnosis. For this purpose, invasive and noninvasive methods are used. Standard 12-lead ECG as one of the noninvasive methods is commonly used in the world at hospitals and clinics. In addition, more sophisticated methods are developed to measure the electrical activity of the heart from the surface of the body, using larger numbers of electrodes known as Body Surface Potential Measurement (BSPM). Invasive methods are also used in special cases to make in vivo measurements. In comparison to non-invasive methods, such as conventional 12-lead system and BSPM, invasive methods require surgical operation to implement the proper electrode network in the desired location. Standard 12-lead system is commonly used in clinical applications for diagnosing and monitoring because of its simplicity in use but it suffers from low spatial resolution of the acquired data. In contrast, BSPM as non-invasive technique, acquires data using large number of electrodes attached to the surface of the body. As a result, the acquired data has better spatial resolution than the 12-lead system. Data obtained from BSPM have significant importance in applications such as localization of the electrical sources in the heart. In this study, we aim to build an analog front end unit to detect the electrical activity of the heart using 10 electrodes connected to the surface of the body. These ten electrodes are recording measurements from the right arm (RA), left arm (LA), and left leg (LL) electrodes, six chest electrodes (V1~V6), and one RLD electrode. Unipolar measurements are used for chest channels (V1~V6). Also, lead I and lead II are constructed via bipolar measurements between (LA, RA) and (LL, RA) pairs, respectively. The analog front end proposed in this thesis is designed to be compatible with 24-bit Sigma Delta analog to digital converter (ADC), so we kept the channels as simple as possible to use the features recommended by the ADC. This unit can be used as the front end of any ECG recording device; it can be the first stage for a 12-lead ECG system, as well as for a BSPM system. Depending on the application requirements, either bipolar or unipolar measurements can be recorded.