Waveform analysis of differential graphs of reconstructed impedance cardiography from healthy individuals

Measurements of cardiac efficiency and internal work of the left ventricle via reconstructed impedance cardiography

Objective. The aim of this study was to investigate methods for measuring the cardiac efficiency (CE) and internal work (IW) of the left ventricle via reconstructed impedance cardiography (RICG).Approach.On the basis of the physiological context and Bernoulli's equation in physics, methods of measuring the CE and IW were proposed. The CE, IW, internal work index (IWI), and other data from 180 healthy adults and 144 patients with cardiovascular disease were measured.Main results. The CE of 180 healthy adults was 22.5 ± 2.2%, and the IWI was 22.3 ± 5.2 J l^-1m^-2. CE decreased with age, and the CE of the younger group (23.5 ± 1.9%) was larger than that of the older group (21.5 ± 1.9%),P < 0.01. The IWI increased with age, and the IWI of the younger group (19.0 ± 3.8 J l^-1m^-2) was smaller than that of the older group (24.8 ± 4.3 J l^-1m^-2),P < 0.01. There were no significant difference in CE (22.4 ± 2.2% and 22.6 ± 2.2%) or in the IWI (21.9 ± 5.1 J l^-1m^-2and 22.6 ± 5.2 J l^-1m^-2) between the male and female groups. The CEs and IWIs of patients with hypertension, coronary heart disease, and heart failure were 17.4 ± 2.4% and 41.8 ± 15.6 J l^-1m^-2, 17.6 ± 3.0% and 35.1 ± 10.4 J l^-1m^-2, and 15.8 ± 3.5% and 42.1 ± 15.6 J l^-1m^-2, respectively. These CEs were all smaller than that (21.6 ± 2.0%) of the healthy contrast groupP < 0.01, while the IWIs were all larger than that (24.6 ± 4.8 J l^-1m^-2) of the healthy contrast group,P < 0.01.Significance.The CEs and IWIs measured in this study may reflect physiological changes in healthy humans and pathogenic conditions in patients with cardiovascular disease.

Waveform analysis of differential graphs of reconstructed impedance cardiography from healthy individuals

Purpose

The aim is to measure and analyze the wave amplitudes and time intervals of differential graphs of reconstructed impedance cardiography (RICG).

Methods

180 adults with normal cardiac function between the ages of 18–78 were included in the study. Six mingled impedance changes on chest surface were simultaneously detected for each subject. The differential graphs of five impedance change components of RICG were obtained through waveform separation and software differentiation. The amplitudes of C, X, O, b waves and time intervals of Q‐b and Q‐C were measured and statistically analyzed.

Results

The amplitudes of C and X waves in PL, PR, AO, and that of C, O, b waves in LV and RV, all decrease as age increases. Wave amplitudes of the female group were bigger than those of the male group (p < .01), while the Q‐C intervals of the female group were shorter than that of the male group (p < .01). Among five impedance change components, the wave amplitude of AO was larger than those of PL and PR (p < .01), and wave amplitudes of PL and PR were bigger than those of LV and RV (p < .01). Q‐C intervals of LV and RV were longer than those of AO, PL and PR (p < .01), while the Q‐b intervals of LV and RV were shorter than the Q‐C intervals of AO, PL, and PR.

Conclusions

The differential graphs of RICG could reflect indirectly the physiological activities and pathological changes of the heart and of the large blood vessels in thorax.