ECG data compression using fast Walsh transform and its clinical acceptability

Data compression techniques can be grouped into three categories, direct and transformation compression and parameter extraction. The principles and details of ECG data compression implementation using fast Walsh transform are presented. Performance evaluation has been made on the basis of compression ratio and visual comparison. To know the extent to which the clinical information preserved in the reconstructed signal, peak and boundary measurements were made on both the reconstructed and original signal, and then compared. As the number of fast Walsh transform coefficients are reduced, the compression ratio increases. At higher compression ratios deviations in the R-peak are found to be higher than those in the other ECG peaks. Peak and boundary measurements reveal clinical acceptability of the compression algorithm, because the errors are quite tolerable. It is also worth noting that artefacts such as electromyographic noise are better eliminated because of filtering, and this also makes the signal compatible to cardiologists for visual examination. The experimental results show that a compression ratio of four is acceptable to preserve the clinical information.