Modulation of Heart Rate Variability in Women Undergoing Ovulation Induction

Estrogens are involved in the modulation of the cardiovascular system, however, their effects in young women remain largely unknown. Women undergoing ovulation induction treatment achieve extremely high estrogen concentrations for a very short period of time. The aim of the present study was to evaluate the effects of acute estrogen elevation on autonomic nervous system modulation of heart rate variability (HRV). A total of 51 women undergoing ovulation induction were studied, HRV was assessed during the estrogen nadir and peak using time domain and power spectral density analysis and Poincaré plot followed by calculation of sympathetic (SNS), parasympathetic (PNS) indices and the Bayevsky stress index (SI). During ovulation, women showed a significant increase in total heart rate variability SDNN, increased mean RR interval, indicating an increase in absolute parasympathetic tone. At the same time, there was a decrease in the heart rate, stress index and SNS index, which can be interpreted as a decrease in the relative sympathetic division of the autonomic nervous system. Ovulation induction caused a significant qualitative restructuring of autonomic regulation: after the completion of induction, the vagus tone assessed by PNS was within the normal range and high values in most women. This indicates that a sharp increase in estrogen levels in women undergoing ovulation induction causes activation of the vagus nerve and a shift in the autonomic balance towards an increase in parasympathetic tone. These results should be taken into account when inducing ovulation in older women and those with chronic diseases.