What is HR

In this chapter the authors described a microcontroller-based MMC/SD card recorder design. It can be used as a reference model to build portable data logging systems. In this case the authors used this design to get the 500 Hz rated samples of Electroardiography (ECG) signal, and evaluate them for R-wave peak detections by using an on-line procedure. The system measures the interbeat times between the consequtive peaks, and records them into a file in the recording media. Heart Rate Variability (HRV) of the two recordings, each has 12-hours length from a healthy and a cardiac disordered man, have been analysed in MATLAB environment. Further analysis has been completed by using the time series of Instantaneous Heart Rates (IHRs) obtained from 48-sets of ECG recordings in the Physionet database. The results support the fact that some of the time and frequency domain parameters reflecting the variability of heart rate can be used as early predictors for some of the heart disorders.