Wavelet Analysis in Impedance Rheocardiography

Impedance cardiography is an inexpensive, noninvasive technique for estimating hemodynamic parameters. Impedance cardiography can be used to obtain the ejection fraction of the left atrium and to monitor systolic time intervals. The wavelet spectrogram provides an illustrative representation of the rheocardiographic measurements. Time-frequency localization of the systolic cardiac wave allows us to define the parameters related to the stroke volume and to control beat-to-beat variations of cardiac parameters in the systolic and diastolic phases of the cardiac cycle. The advantage of the wavelet-based approach is demonstrated by an example of determining the stroke volume variation during the respiratory cycle. Wavelet-based processing of impedance cardiography signals reduces the influence of artifacts and the interference of breathing modulation and displays the morphological features of cardiac cycles. In particular, the advantages of the method are considered by the isometric test of patients with hypertension.