A method to assess heart rate variability in neonate rats: validation in normotensive and hypertensive animals.

S.C.F Freitas,M.R.H Dutra,M.C Irigoyen,C Paixão Dos Santos,M Veras,A Arnold,K De Angelis,F.F Stoyell-Conti

doi:10.1590/1414-431x20209493

Abstract

Several studies have focused on the heart rate variability (HRV) of murine species, while studies discussing HRV in murine neonates and infants remain scarce, since recording hemodynamic signals through invasive methods in small animals has been found to be quite challenging. Thus, this study aimed at describing and validating a novel method to assess HRV in newborn rats. An electrocardiogram (ECG) system was used to determine RR intervals in awake newborns and evaluate HRV in normotensive (Wistar) and hypertensive (SHR) neonate rats. After birth, ECG was recorded in the awake newborns, and they were allowed to rest on a heated surface, restricted only by the weight of the adhesive ECG electrodes. The electrodes were cut and adapted to provide more comfort to the animal, and gently placed on the newborn's skin. RR intervals were recorded over a 30-min period using an ECG system together with LabChart software (4 KHz). Three sequences of 5 min each from the ECG recording period were analyzed in time and frequency domains, using CardioSeries software. ECG data resulted in a clearly interpretable signal that was used to generate an RR interval sequence through time for the analysis of HRV. SHR neonates presented increased cardiac sympathovagal balance compared to Wistar neonates (low frequency/high frequency: 3.85±0.71 vs 0.90±0.09). In conclusion, the ECG setup here described may be used to record RR intervals to assess HRV in neonate rats, thus detecting early impairment of HRV in hypertensive newborns.

Highlights

When observed on a beat-to-beat- basis, cardiovascular variables exhibit rhythmical fluctuations in their mean values even in the absence of any external stimulus [1]
We described the use of an ECG setup for the acquisition of R intervals (RR) interval to assess heart rate variability (HRV) in neonate rats
This recording showed clearly interpretable ECG waves, generating an RR interval sequence through time and making it possible to assess HRV using a specialized software (CardioSeries). This demonstrates the ease of accurately recording RR intervals for HRV assessment in neonates using the protocol proposed in this study

Summary

Introduction

When observed on a beat-to-beat- basis, cardiovascular variables exhibit rhythmical fluctuations in their mean values even in the absence of any external stimulus [1]. The quality of the signal, the R-to-R intervals (RR) gathered from the electrocardiogram (ECG), and the pulse interval obtained from direct arterial pressure recording are critical components for HRV analysis In this sense, the acquisition of biological signals in small animals, by invasive arterial pressure procedures, is quite challenging due to the need of specialized surgical skills and expensive recording equipment [4]. The acquisition of biological signals in small animals, by invasive arterial pressure procedures, is quite challenging due to the need of specialized surgical skills and expensive recording equipment [4] For this reason, the use of an ECG platform is a viable alternative methodology to obtain RR interval in neonates and assess cardiac autonomic modulation. We described the use of an ECG setup for the acquisition of RR interval to assess HRV in neonate rats

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Conclusion