Detection of higher frequency components at mid-QRS stage of electrocardiogram--A digital filtering approach and its possible relevance to myocardial tissue characterization

In order to detect very minute energy, if any, of higher frequency range at the mid-QRS stage of an electrocardiographic signal, frequency domain analysis and three-dimensional presentation of its outcome were carried out. A simulation-averaged electrocardiographic signal underwent digital filtering using techniques of narrow band-passing characteristics. The set of frequency component curves with stepwise increasing center frequency of band-passing was normalized so that higher frequency components with very low energy were especially emphasized. The higher frequency components at the mid-QRS stage were clearly present with special features (plural peaks on frequency component curves) in many of the patient groups with coronary heart disease and in none with such features among the normals, indicating the possible usefulness of this approach for electrical 'tissue characterization' of cardiac muscles.