A new analysis of heart rate variability in the assessment of fetal parasympathetic activity: An experimental study in a fetal sheep model

Abstract

Analysis of heart rate variability (HRV) is a recognized tool in the assessment of autonomic nervous system (ANS) activity. Indeed, both time and spectral analysis techniques enable us to obtain indexes that are related to the way the ANS regulates the heart rate. However, these techniques are limited in terms of the lack of thresholds of the numerical indexes, which is primarily due to high inter-subject variability. We proposed a new fetal HRV analysis method related to the parasympathetic activity of the ANS. The aim of this study was to evaluate the performance of our method compared to commonly used HRV analysis, with regard to i) the ability to detect changes in ANS activity and ii) inter-subject variability. This study was performed in seven sheep fetuses. In order to evaluate the sensitivity and specificity of our index in evaluating parasympathetic activity, we directly administered 2.5 mg intravenous atropine, to inhibit parasympathetic tone, and 5 mg propranolol to block sympathetic activity. Our index, as well as time analysis (root mean square of the successive differences; RMSSD) and spectral analysis (high frequency (HF) and low frequency (LF) spectral components obtained via fast Fourier transform), were measured before and after injection. Inter-subject variability was estimated by the coefficient of variance (%CV). In order to evaluate the ability of HRV parameters to detect fetal parasympathetic decrease, we also estimated the effect size for each HRV parameter before and after injections. As expected, our index, the HF spectral component, and the RMSSD were reduced after the atropine injection. Moreover, our index presented a higher effect size. The %CV was far lower for our index than for RMSSD, HF, and LF. Although LF decreased after propranolol administration, fetal stress index, RMSSD, and HF were not significantly different, confirming the fact that those indexes are specific to the parasympathetic nervous system. In conclusion, our method appeared to be effective in detecting parasympathetic inhibition. Moreover, inter-subject variability was much lower, and effect size higher, with our method compared to other HRV analysis methods.

Parasympathetic nervous system response to acidosis: Evaluation in an experimental fetal sheep model

“…We developed a new index, the FSI, based on our previous work in adults and newborns. We demonstrated that the FSI was associated with lower interindividual variability and a higher effect size than commonly used HRV analysis methods, suggesting that the index could better detect a decrease in parasympathetic tone . In a preliminary study, we showed a correlation between the FSI and fetal acidosis in a continuous occlusion model, demonstrating proof of concept for the FSI.…”

“…Our team proposes a new index, the fetal stress index (FSI), based on an original method of HRV analysis combining spectral and time domain analyses. In a previous experimental study, we showed that this index was sensitive and specific for fluctuations of parasympathetic nervous system activity and had lower interindividual variability and a higher ability to detect changes in parasympathetic nervous system activity compared with commonly used methods of measuring HRV . We also demonstrated that this index was correlated with fetal pH …”

Correlation of a new index reflecting the fluctuation of parasympathetic tone and fetal acidosis in an experimental study in a sheep model

“…Eleven near-term pregnant sheep (128 +/- 2 days gestational age, term = 145 days) underwent surgical procedure. Anesthetics and surgical techniques protocols followed those previously described by our team or in the literature [ 14 – 16 ]. Pregnant Charmoise sheep (INRA, Leudeville, France) were fasted 24 h before surgery.…”

“…Our hypothesis is that, because of its reflecting parasympathetic activity, it makes it possible to detect fetuses at risk of acidosis. In a previous study, we shown that this index had a lower inter-subject variability, and a higher effect size compared to other HRV analysis methods [ 14 ].…”

Fundus Photography, Fundus Fluorescein Angiography, and Optical Coherence Tomography of Healthy Cynomolgus Monkey, New Zealand Rabbit, Sprague Dawley Rat, and BALB/c Mouse Retina

“…Qualitative and quantitative changes in anatomical structure and physiological function are the basis of disease research, so accurate descriptions of baseline properties are essential. Numerous reports have examined normal parameters for blood, heart, brain, liver, kidney, and other large organs among common experimental model animals [1][2][3][4][5], but few have examined eye structure and function in different models for ophthalmology research. A complete set of anatomic and physiological parameters for speci c experimental animals will be invaluable for choosing the optimal model, preparation technique, and measurement technology.…”