A new electric method for non-invasive continuous monitoring of stroke volume and ventricular volume-time curves

Abstract

BackgroundIn this paper a new non-invasive, operator-free, continuous ventricular stroke volume monitoring device (Hemodynamic Cardiac Profiler, HCP) is presented, that measures the average stroke volume (SV) for each period of 20 seconds, as well as ventricular volume-time curves for each cardiac cycle, using a new electric method (Ventricular Field Recognition) with six independent electrode pairs distributed over the frontal thoracic skin. In contrast to existing non-invasive electric methods, our method does not use the algorithms of impedance or bioreactance cardiography. Instead, our method is based on specific 2D spatial patterns on the thoracic skin, representing the distribution, over the thorax, of changes in the applied current field caused by cardiac volume changes during the cardiac cycle. Since total heart volume variation during the cardiac cycle is a poor indicator for ventricular stroke volume, our HCP separates atrial filling effects from ventricular filling effects, and retrieves the volume changes of only the ventricles.Methodsex-vivo experiments on a post-mortem human heart have been performed to measure the effects of increasing the blood volume inside the ventricles in isolation, leaving the atrial volume invariant (which can not be done in-vivo). These effects have been measured as a specific 2D pattern of voltage changes on the thoracic skin. Furthermore, a working prototype of the HCP has been developed that uses these ex-vivo results in an algorithm to decompose voltage changes, that were measured in-vivo by the HCP on the thoracic skin of a human volunteer, into an atrial component and a ventricular component, in almost real-time (with a delay of maximally 39 seconds). The HCP prototype has been tested in-vivo on 7 human volunteers, using G-suit inflation and deflation to provoke stroke volume changes, and LVot Doppler as a reference technique.ResultsThe ex-vivo measurements showed that ventricular filling caused a pattern over the thorax quite distinct from that of atrial filling. The in-vivo tests of the HCP with LVot Doppler resulted in a Pearson’s correlation of R = 0.892, and Bland-Altman plotting of SV yielded a mean bias of -1.6 ml and 2SD =14.8 ml.ConclusionsThe results indicate that the HCP was able to track the changes in ventricular stroke volume reliably. Furthermore, the HCP produced ventricular volume-time curves that were consistent with the literature, and may be a diagnostic tool as well.

Non-invasive measurement of volume–time curves in patients with mitral regurgitation and in healthy volunteers, using a new operator-independent screening tool

“…An algorithm has been designed to distill the ΔV (ven) (t) (i.e. the ventricular VTC) from the equation above, using the measured M(t) − M(0) in combination with the known S (atr) and S (ven) as the input (Konings et al 2012). The HCP system performs this calculation automatically and continuously.…”

“…The principle of operation of the HCP has been described in our previous paper (Konings et al 2012). In summary, a very weak, patient-safe, high-frequency AC current of frequency f (between 58 kHz and 90 kHz), with an amplitude of 8 mA pp , was applied to the thorax, using standard ECG skin electrodes (Nutrode-P20M0 and Nutrode-P10M0 pre-gelled, GE Healthcare, United Kingdom) positioned on the legs and above the left and right clavicle.…”

“…However, in previous publications, we have presented a new, operator-independent and non-invasive method for continuous measurement of ventricular stroke volume using a highfrequency electric current: the hemodynamic cardiac profiler (HCP). We have shown the ability of the HCP to measure the LV stroke volume in an animal study (Konings et al 2011), and have described the principle of operation of the HCP in mathematical detail (Konings et al 2012), pointing at the possibility to measure VTCs with the HCP. In the present paper the focus will be completely on the generation of VTCs by the HCP, and the cardiologic parameters that can be extracted from these VTCs.…”

The hemodynamic cardiac profiler volume-time curves and related parameters: an MRI validation study

“…As previously demonstrated, the 'Hemodynamic Cardiac Profiler' (HCP) is able to measure volume-time curves (VTCs) of the ventricles (i.e. the volume of the blood inside the ventricles as function of time during a single cardiac cycle) in a wide range of settings (Konings et al 2012, Konings et al 2017. The HCP is a low-cost, noninvasive system, specifically designed to be easy to use, and requires no trained operator for its operation, i.e.…”

Hemodynamic effects of epinephrine in rats: evaluation by impedance cardiography

“…This is associated with left atrial hypertension as well as a decrease in left ventricular end-diastolic diameter (19). The accurate measurement of hemodynamic parameters of these side effects and their changes in response to physiological or pharmacological stimuli is an important factor in evaluation of the heart mechanical effi ciency, especially for hemodynamic management of critically ill patients and evaluation of postoperative treatment progress in the intensive care units (20)(21).…”