ELECTRICAL ACTIVITY OF THE HUMAN HEART DURING THE PERIOD OF VENTRICULAR DEPOLARIZATION UNDER ACUTE NORMOBARIC HYPOXIA

Abstract

Background. The effect of acute hypoxia on the human heart leads to deterioration of the heart function, this is reflected in an increase of the heterogeneity of the depolarization process, which is difficult to reveal when using a traditional ECG.
 Purpose. To investigate the electrical activity of the heart during the ventricular depolarization on the thorax surface under the exposure of acute normobaric hypoxia using multichannel ECG mapping.
 Material and methods. The electrical activity of the heart in apparently healthy young men (20±1 years) was studied during ventricular depolarization under exposure of acute normobaric hypoxia using cardioelectrotopography. Unipolar ECGs were recorded from 64 electrodes on the surface of the chest, simultaneously with bipolar ECGs in limb leads and the amplitudes of R and S waves from the surface electrodes localized in positions V1 and V5 of the traditional ECG were evaluated.
 Results. It was revealed that during hypoxia, in comparison with the initial state, the pattern of distribution and the spatio-temporal dynamics of positive and negative cardiac potentials reflecting the sequence of myocardial activation on the torso surface did not change significantly and were typical for the period of ventricular depolarization of the healthy person. A decrease in the amplitudes of the maximum extrema of cardiac electric potentials, the amplitudes of the SV1 and RV5 waves at hypoxic exposure was revealed: the amplitude of the maximum decreased from 1.88±0.58 mV in the initial state to 1.83±0.55 mV at hypoxia, the minimum – from -2.08±0.76 mV to -1.85±0.73 mV, the SV1 wave from -1.28±0.25 mV to -1.17±0.18 mV, RV5 wave from 1.21±0.25 mV to 1.05±0.29 mV, respectively, while the duration of ventricular depolarization did not change statistically significantly.
 Conclusion. Under hypoxic exposure, the examined persons showed a significant decrease in the amplitudes of the maximum extrema of the electric field of the heart, a direct correlation between changes in the amplitudes of the positive extremum and the RV5 wave, with practically unchanged duration of ventricular depolarization and dynamics of the distribution of cardioelectric potentials.