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

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

Mapeamento do Potencial da Superfície Corporal durante a Despolarização Ventricular em Atletas com Intervalo PQ Prolongado após Exercício

Resumo Fundamento: O prolongamento do intervalo PQ, geralmente associado a um atraso na condução atrioventricular, pode estar relacionado a alterações na propagação do impulso intraventricular. Objetivo: Avaliar, por meio do mapeamento do potencial de superfície corporal (BSPM), o processo de despolarização ventricular em atletas com intervalos PQ prolongados em repouso e após o exercício. Métodos: O estudo incluiu 7 esquiadores cross-country com intervalo PQ superior a 200 ms (grupo PQ Prolongado) e 7 com intervalo PQ inferior a 200 ms (grupo PQ Normal). O BSPM de 64 derivações unipolares do tronco foi realizado antes (Pré-Ex) e após o teste ergométrico de bicicleta (Pós-Ex). Mapas equipotenciais da superfície corporal foram analisados durante a despolarização ventricular. O nível de significância foi de 5%. Resultados: Comparado com atletas com PQ Normal, o primeiro e o segundo períodos de posição estável dos potenciais cardíacos na superfície do tronco foram mais longos, e a formação da distribuição de potencial “sela” ocorreu mais tarde, no Pré-Ex, nos atletas com PQ Prolongado. No Pós-Ex, o grupo PQ Prolongado apresentou um encurtamento do primeiro e segundo períodos de distribuições de potencial estáveis e uma diminuição no tempo de aparecimento do fenômeno “sela” em relação ao Pré-Ex (para valores próximos aos do Normal -Grupo PQ). Além disso, no Pós-Ex, a primeira inversão das distribuições de potencial e a duração total da despolarização ventricular em atletas com PQ Prolongado diminuíram em comparação com o Pré-Ex e com valores semelhantes em atletas com PQ Normal. Em comparação com atletas com PQ Normal, a segunda inversão foi mais longa no Pré-Ex e Pós-Ex em atletas com PQ Prolongado. Conclusão: Atletas com PQ prolongado apresentaram diferenças significativas nas características temporais do BSPM durante a despolarização ventricular, tanto em repouso quanto após o exercício, em comparação com atletas com PQ normal

Cardioelectrotopographic Assessment of the Ventricular Repolarization in Racing Skiers and Powerlifters

The article determines significant amplitude-temporal parameters of the heart electric fxield distinctions in the course of ventricular repolarization in sportsmen training different physical qualities – strength (powerlifters) and endurance (racing skiers)

Racing Skiers and Swimmers’ Heart Electric Field during Ventricular Depolarization at Recovery Period after Moderate and Submaximal Physical Load

The article presents the results of cardioelectrotopographic investigation of racing skiers and swimmers’ heart electric activity during ventricular depolarization at recovery period after moderate and submaximal physical load. Changes in ventricular depolarization time and ventricular depolarization phases ratio due to longer duration of the first and second cardioelectric potential inversions on the chest surface in racing skiers and less duration of the depolarization initial phase in swimmers were detected after moderate and submaximal loa

Morphometric Parameters, Contractility and Architecture of the Left Ventricle Myocardium in Pigs

This study aims to reveal the interrelations found within the architecture of the muscular fibers, the morphometric parameters and contractility of the left ventricular myocardium in the Landrace breed of conventional pigs. The left ventricular morphometric parameters were investigated at three levels (basal, middle, apical) utilizing echocardiography, myocardial contractility was estimated by the ejection fraction, fractional shortening and fractional thickening. The fiber architecture of the working myocardium was studied following the method of the layer-by-layer splitting of muscular fibers. The fibers ofthe superficial and deep layers of the left ventricle showed an oblique orientation, while the muscular fibers of the middle layer were distinguishable as high-lying and low-lying fibers. During the cardiac cycle, the greatest reduction in the transverse dimension and the greatest thickening of the walls were observed in the middle level when compared with the basal and apical levels, that is related with more thick layer of muscular circumferential fibers in the middle section of the ventricle and large papillary muscles. A low contractile ability of the left ventricle myocardium was revealed in pigs