Improved modified AZTEC technique for ECG data compression: Effect of length of parabolic filter on reconstructed signal

The existing techniques for electrocardiogram (ECG) data compression have been classified into three major categories, namely, direct data compression (DDC), transformation compression (TC) and parameter extraction compression (PEC). This paper deals with an efficient DDC algorithm, which has been developed over existing modified Amplitude Zone Time Epoch Coding (AZTEC) technique, named as improved modified AZTEC and tested on Common Standard for quantitative Electrocardiography (CSE) database. The performance has been evaluated on the basis of compression ratio (CR), percent-root-mean-square difference (PRD) and fidelity of the reconstructed signal. A comparison of the wavelet-derived features of compressed and original signals has been used for performance evaluation of the compressed signal. In this paper, the effect of length of least-square polynomial smoothing filters, i.e., parabolic filters, on the reconstructed signal has been analyzed. The use of 7-point parabolic filter has been found to improve the percent-root-mean-square difference (PRD), i.e. lower PRD, compared to reconstruction process of ECG signal without filter. It is also observed that the use of parabolic filters rejects high frequency noise, which is reflected in the form of reduced electromyographic noise.