Use of Phase Spectral Information in Assessment of Frequency Contents of ECG Waveforms

The electrocardiogram of a healthy subject consists of three waveforms which reflect electrical activity of the myocardium, the P-wave, the QRS-complex and T-wave. An important feature of these waveforms is their frequency content. A practical recorded waveform comprises both a random component (noise and hum) and a deterministic component (the signal). A recently introduced method for the assessment of the bandwidth of time locked waveforms is the analysis of the standard deviation ¿¿ of the phase spectrum from a number of waveforms. The standard deviation is shown to be low for frequency components which are part of the signal, and high (in theory ¿¿/¿¿3) for random components. The theoretical validity of the method as well as its practical limitations are discussed. Examples of the applicability of the method are given, together with a discussion of the results and suggestions for overcoming some of the limitations of the basic method.