Systematic variability in ICG recordings results in ICG complex subtypes – steps towards the enhancement of ICG characterization

Abstract

The quality of an impedance cardiography (ICG) signal critically impacts the calculation of hemodynamic parameters. These calculations depend solely on the identification of ICG characteristic points on the ABEXYOZ complex. Unfortunately, contrary to the relatively constant morphology of the PQRST complex in electrocardiography, the waveform morphology of ICG data is far from stationary, which causes difficulties in the accuracy of the automated detection of characteristic ICG points. This study evaluated ICG recordings obtained from 10 volunteers. The results indicate that there are several different waveforms for the ABEXYOZ complex; there are up to five clearly distinct waveforms for the ABEXYOZ complex in addition to those that are typically reported. The differences between waveform types increased the difficulty of detecting ICG points. To accurately detect all ICG points, the ABEXYOZ complex should be analyzed according to the corresponding waveform type. Acronyms and abbreviations ICG: impedance cardiography ΔZ: impedance change signal dZ/dt: the first derivative of the impedance change signal dZ/dtmax: the maximum amplitude of the dZ/dt signal, also noted as E or C points LVET (or ET): left ventricular ejection time IVRT: isovolumic relaxation time SV: stroke volume CO: cardiac output ABEXYOZ complex: characteristic points on the dZ/dt signal that constitute one heart cycle ECG: electrocardiography PEP: pre-ejection period FT: ventricular filling time STR: systolic time ratio PQRST: complex in the ECG signal, from P over Q, R and S to T ABEX: segment of an ABEXYOZ complex from A over B and E to X YOZ: segment of an ABEXYOZ complex from Y over O to Z FEM: Finite Element Method

Fundamentals, Recent Advances, and Future Challenges in Bioimpedance Devices for Healthcare Applications

“…Transthoracic impedance is modulated by cardiorespiratory activity, such that a decrease in impedance can be related to an increase of blood flow. The derivative of impedance (dZ/dt) contains a set of seven points (A, B, E, X, Y, O, Z, see Figure 17) related to cardiodynamic events [217]. Hence, cardiovascular condition and diverse hemodynamic parameters such as heart rate, cardiac volume, stroke volume, cardiac output, vascular resistance, velocity index, or thoracic fluid content, among others, can be noninvasively monitored against time by extracting characteristic points and periods of the dZ/dt signal through ICG [218].…”

ReBeatICG: Real-time Low-Complexity Beat-to-beat Impedance Cardiogram Delineation Algorithm

“…However, its identification can be difficult due to variations in the ICG signal's morphology. Thus, different definitions have been proposed [4], [17]- [19].…”

“…It is important to note that there are many variations in the morphology of the ICG signals [4], [17]. In Fig.…”

Age-related differences in the morphology of the impedance cardiography signal

“…Although the ICG curve is defined in the literature, the shape of representative ICG curves of apparently healthy subjects can have substantial differences between publications, comparing figure 1 to figures in for example [Cybulski, 2011;Marquez et al, 2013;Carvalho et al 2011]. The issue of differences in ICG waveforms and complexes of characteristic points is very well highlighted in Ermishkin et al [2012] and in Benouar et al [2018], also demonstrating that the ICG waveform morphology is far from stationary.…”

“…The issue of differences in ICG waveforms and complexes of characteristic points is very well highlighted in Ermishkin et al . [2012] and in Benouar et al . [2018] , also demonstrating that the ICG waveform morphology is far from stationary.…”