LABORATORY-INSTRUMENTAL COMPARISONS OF CARDIAC RHYTHM VARIABILITY IN NEWBORNS FOLLOWING HYPOXIA

Abstract

Summary Introduction. Determination of the state of autonomic regulation of cardiac activity has been widely used in various disorders in neonatal practice. Hypoxia is known to have a significant adverse effect on myocardial function and autonomic cardiac control processes. Early detection of the development of posthypoxic damage to the autonomic nervous regulation of cardiac activity by analyzing the variability of cardiac rhythm and finding its relationship with other characteristics of cardiac rhythm variability (CRV) may be useful for determining the subsequent therapeutic approach for such infants. The aim of the study is to improve early diagnosis of posthypoxic myocardial damage by studying cardiac rhythm variability of (CRV) in newborns following hypoxia and comparing its characteristics with laboratory-instrumental indicators of cardiovascular system. Material and methods. 187 newborns were examined in the early neonatal period. The study involved assessment of medical records, biochemical blood test (AST, ALT, KFK, KFK-MV, LDH, GGTF),daily monitoring of ECG according to Holter (HMEGG) with determination of the main temporal indicators of heart rate variability, Doppler echocardiography (DEchoCG) and statistical processing. Results and discussion. Depending on the Apgar scale at the 1st minute, the children were divided into 2 main groups: newborns with Apgar score less than 6 points which comprised the 1st group (n=132), newborns with Apgar score of 7 points or more were included into the 2nd group (n=55). Depending on the gestational peculiarities at birth, children were subdivided into subgroups of full–term and preterm infants: group 1a (n=15) were full–term infants with hypoxia at birth, group 1b (n=117) were premature newborns with hypoxia at birth, group 2a (n=43) were full– term neonates without hypoxia at birth, group 2b (n=12) were prematurely born without hypoxia at birth. According to HMEGG findings, the mean, mean minimum and mean maximum heart rates were higher in the group of infants who underwent hypoxia, with the highest rates in the group of premature infants. Circadian index scores were lower in the group of newborns who underwent hypoxia, with the lowest in the group of preterm infants. Assessment of correlation dependencies of CRV time parameters with laboratory parameters and DECHOCG parameters showed that SDANN had the highest percentage of relationships with laboratory and instrumental indicators of CVS status. With the parameters of DECHOCG in all groups, rMSSD and pNN50 indicators had the highest number of relationships, which most fully characterized the state of hemodynamics in the group of newborns with existing disorders of adaptation at birth secondary to hypoxic events (group 1) and in the subgroup of premature children (group 1b). SDNN was associated with CPK-MB and gammaglutamyltransferase values, as an indicator of the antioxidant system of body protection in newborns with impaired adaptation at birth following hypoxia, including in the group of premature infants. Conclusions. Prematurely born children who undergo hypoxia have a more pronounced autonomic imbalance in the regulation of cardiac activity. Comprehensive CRV assessment with determination of all parameters characterizing the state of sympathetic and parasympathetic regulation in comparison with biochemical parameters of CVS and DECHOCG will allow to improve the early diagnosis of posthypoxic myocardial injury and to develop further approach of patient management.