Development of ambulatory ECG monitoring device with ST shape classification

In this paper, we describe the hardware configuration for ambulatory ECG monitoring device and the algorithm for detection of ST shape change. Ambulatory ECG recordings are available for diagnosis of heart diseases such as myocardial infarction, arrhythmia, etc. It especially is important to detect the transient ECG pattern changes. The detection of transient ST change caused by myocardial ischemia is one of the reasons why ambulatory ECG monitoring system is necessary. We designed a small-size portable ECG device that consisted of instrumentation amplifier, multiplexer, micro-controller, filter and transmitter module. The device measures ECG with four electrodes in the body and transmits the signal to receiver connected in PC by digital radio way. The developed algorithm detects the ST level change, and then classifies the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by comparing the slopes between the reference ST type and the least square curve. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is. And, the result of analysis is used to make control signal that decides when ECG recording begin and when stop.