Wearable Sensor Node for Cardiac Ischemia Detection

Detection of cardiac ischemia based on early repolarization ECG markers has been widely recognized since three decades. It is also employed as a safety marker in exercise testing and cardiac rehabilitation. It assumes a standardized load applied to a patient in laboratory conditions, which diminishes patients’ responsiveness and lowers the medical outcome statistics. A remedy consists in detecting ischemia markers during daily living activities in context of instantaneous physical load. Patients more willingly participate in diagnostics or rehabilitation, but the procedure requires specialized sensors and processors of ECG dedicated to use in domestic conditions. To this point we designed a small and lightweight autonomous twolead ECG sensor node including heart rate and ST-segment processing algorithm and secure Bluetooth Low Energy connectivity to a supervising Wearable Sensor Network. In laboratory exercise tests with 50 ischemic patients the sensor issued alerts well coinciding with the output of a standard 12-lead system (with 2 fp and 1 fn cases). Moreover, in a two-lead setup the electrodes can be randomly applied to the skin in location best corresponding the ischemic region. Low power-oriented design and low transmission duty cycle result in continuous operation of the sensor for over a month with one coin battery.