Controlling the Distortions Distribution in a Wavelet Packet-Based ECG Compression

The paper presents a new approach to the ECG compression algorithms. The idea of non-equal density of medical information in the electrocardiogram yields the new design guidelines for a compression system. The distortions of reconstructed signal, considered as unavoidable result of data reduction in other traditional systems, are now subject to control. The temporal distribution of distortions, within the confines of a heart evolution, may be designed as signal-feature dependant, application-dependant or even controlled by the doctor. Being similar in technical aspect, the resulting compression algorithms differ in favoring a particular zone in the signal accordingly to the physiological expectations. The compression ratio, the usual key feature for assessment of the compression efficiency, gives priority to the signal quality that is indisputably essential for electrodiagnostic applications. Controlling the distortions temporal distribution is achieved in time-frequency domain by means of a “function of interest” containing information on the local diagnostic importance of the ECG. A wavelet packet-based compression algorithm is also proposed and tested in the paper.