Assessment of Systolic Heart Function by Wavelet Analysis of the Impedance Cardiogram

Abstract

Impedance cardiography (ICG) can be used to obtain one of the key hemodynamic parameters - stroke volume (SV). The SV is proportional to the left ventricular ejection time (LVET) and the maximum value of the first derivative of the recorded impedance (E wave) during the given cycle. Traditional ICG technique does not enable unambiguous detection of the LVET time between onset of the aortic valve opening and closing process. Objective of this work is investigation the possibilities of wavelet analysis (WA) approach to determine the parameters of the SV, in particular LVET. We can define LVET as the scale corresponding to the E wave maximum on 2D wavelet representation of the ICG data. Wavelet estimation of the LVET is well correlated (0.8) with the time interval between first and second heart sound, defined with usage of phonocardiogram. The proposed approach demonstrates the ability of ICG-WA technique to adequate assessment of SV parameters, including LVET and can be used in clinical practice.