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In order to detect left ventricular systolic function and diastolic time intervals using a new improved bioimpedance polyrheocardiographic system (BPCS), 110 healthy subjects and 128 patients with myocardial infarction were examined. Twenty-four simultaneous measurements of cardiac output by thermodilution and BPCS were performed in 11 patients with complicated acute left ventricular failure. Studies demonstrated a high degree of correlation (r = 0.91, p < 0.001). The correlation between the methods of using signals of the second derivative and the subtracted first derivative waveform of BPCS and continuous-wave Doppler echocardiography of systolic and diastolic time intervals was studies in 51 patients. The methods were closely correlated, especially with respect to left ventricular ejection time (r = 0.95), isovolumic relaxation time (r = 0.85), time to peak filling (r = 0.90), and deceleration of rapid filling time (r = 0.91). New bioimpedance hemodynamic parameters such as peak volume acceleration of ejection (PVAE) and peak power ejection (PPE) in patients with heart failure (NYHA Class I-III) were studied. Significant reductions of PVAE and PPE in groups of patients with marked progression of heart failure were noted. These results have demonstrated that BPCS is a noninvasive, simple accurate method of assessment of left ventricular systolic function and diastolic time intervals.

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Abstract. 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. CONCLUSION: The proposed approach demonstrates the ability of ICG-WT technique for adequate assessment of SV parameters, including cardiac time intervals.