Assessment of cardiac time intervals by wavelet transform of the impedance cardiogram.
BACKGROUND
Impedance cardiography (ICG) is an inexpensive, noninvasive technique for estimating hemodynamic parameters. ICG can be used to obtain the ejection fraction of the left atrium and to monitor systolic time intervals. Traditional ICG technique does not enable unambiguous detection of the left ventricle ejection time (LVET) and the time relationships between specific marker points.


OBJECTIVE
This work aims to approbate a new approach for ICG signal processing using wavelet transform (WT) and to investigate the possibilities of this approach for determination of the parameters which are related to the stroke volume (SV), in particular LVET.


METHODS
Thoracic tetrapolar polyrheocardiography method for simultaneous registration of ECG, ICG and phonocardiograms has been used. A control group consisted of eight healthy men aged 20-25 years. In addition, four patients with essential hypertension participated in the study. Wavelet representation of the ICG data produced local maxima in a two dimensional distribution of the wavelet coefficient. Each extremum point was characterized by the amplitude, scale and time, which determine SV.


RESULTS
LVET was defined as the scale corresponding to the E-wave maximum related to the systolic phase of the cardiac cycle. Also, we defined the initial systolic time interval (ISTI) as the time interval between R peak in the ECG and E-wave maximum on the wavelet plane. During functional test LVET and ISTI values defined by WT demonstrated a proper hemodynamic response to loading for the control group and patients with essential hypertension.


CONCLUSIONS
The proposed approach demonstrates the ability of ICG-WT technique for adequate assessment of SV parameters, including cardiac time intervals.
Institute of Continuous Media Mechanics, Perm, Russia.
Rodion
R
Stepanov
Institute of Continuous Media Mechanics, Perm, Russia.
Sergey
S
Podtaev
Institute of Continuous Media Mechanics, Perm, Russia.|Department of Introduction into Internal Diseases, Perm State Medical Academy, Perm, Russia.
Andrey
A
Dumler
Institute of Continuous Media Mechanics, Perm, Russia.|Department of Introduction into Internal Diseases, Perm State Medical Academy, Perm, Russia.
Sergey
S
Chugainov
D000328:Adult; D002307:Cardiography, Impedance; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D013318:Stroke Volume; D013599:Systole / Q000502:physiology*; D013997:Time Factors; D058067:Wavelet Analysis; D055815:Young Adult
Impedance cardiography; hemodynamic parameters; wavelet transform