The Precordial Electrical Impedance Methods Possibilities in the Evaluation of Local Heart Chambers Contractility
The paper considers the possibility of precordial electrical impedance measurements in the evaluation of the heart chambers mechanical activity. It is shown that the precordial electrode systems allow to analyze the heart wall movement in systole of the a
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BMSTU/Biomedical Engineering Department, Moscow, Russian Federation 2 I.M. Sechenov FMSMU, Moscow, Russian Federation
Abstract — The paper considers the possibility of precordial electrical impedance measurements in the evaluation of the heart chambers mechanical activity. It is shown that the precordial electrode systems allow to analyze the heart wall movement in systole of the atria and ventricles. In particular, radial mapping method allows to estimate the ventricles walls local movements. Keywords— electro impedance, precordial rheocardiography, atrium, ventricles, mechanical activity.
I.
INTRODUCTION
Electrical impedance techniques of the heart measurements allow estimate the volume characteristics and myocardial contractility in monitor mode. The possibilities of this method are used for the diagnosis of chronic heart failure [1], during medical treatment, controlling hemodynamics during anesthesia, as well as in other clinical applications. The transition from the traditional transthoracic measurements in precordial electrical impedance techniques provides an opportunity to obtain new information about the parameters of cardiac activity, taking into account the individual patient.
II.
BACKGROUND
The gold standard in main way heart diagnosis are ECG and ultrasonic investigations. But these methods can’t get all information about heart working. E.g. right atrial activity analysis is often a major problem both in ultrasonic studies and in the analysis of MRI or CT data. There are no systems that can control mechanical heart activity in monitor mode. Today conventional transthoracic electrical impedance signal forming mechanisms are changes in the heart and the aorta blood volume and the erythrocytes orientation changes during ventricular systole [2]. But it should be noted that tissues surrounding the heart also affect to the measurements. The first is lungs and soft tissue. To minimize the impact of changes in lung resistivity when breathing electrical impedance measurements should be carried out on the patient's exhalation. Patient should be © Springer Nature Singapore Pte Ltd. 2018 H. Eskola et al. (eds.), EMBEC & NBC 2017, IFMBE Proceedings 65, DOI: 10.1007/978-981-10-5122-7_190
in the supine position. The lungs resistivity during exhalation is about 4-7 Ohm*m, and during inspiration about 11-23 Ohm*m [3]. On the exhalation lung tissue conductivity parameters are close to the parameters of the soft tissue surrounding the heart. In this case the blood resistivity is different from other the patient's chest tissues. This difference allows to simplify inverse task of hemodynamic parameters calculation according to precordial electrical impedance measurements. To move from integrated signals reflect simultaneously changes in the heart and the aorta blood volume, change the erythrocytes orientation changes, and the chest tissues resistance changing, the electrode systems may be located in the heart projection area to the chest surface (Fig.1). With this electrode systems arrangement received signals rep
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