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Heart rate variability in different phases of menstrual cycle among healthy medical students of a teaching institution, South India

Background: Cardiac autonomic function in females depends on the fluctuations in the level of endogenous sex hormones during menstrual cycle. Heart rate variability (HRV) is a non-invasive test that helps to assess the function autonomic nervous system mainly the sympathovagal balance. 
 
Aims and Objective: The aim of the study was to evaluate the HRV in different phases of menstrual cycle in healthy females of a teaching institution, South India. 
 
Materials and Methods: A cross-sectional study was conducted among 19 regularly menstruating females in the age group of 1824 years of age after taking informed consent and institutional ethical clearance. Sympathovagal balance was assessed using HRV analysis in the proliferative and secretory phases of menstrual cycle. 
 
Results: This study observed an increase in low frequency (LF) in normalized units domain as well as/high frequency (HF) ratio in the secretory phase and an increase in the HF normalized units domain in the proliferative phase, though statistically non-significant. A significant increase in the resting heart rate was noted among the secretory phase compared to the proliferative phase of menstrual cycle (P < 0.001). 
 
Conclusion: An increased sympathetic activity during secretory phase and an increased vagal activity in the proliferative phase were observed, which could be explained due to the fluctuating levels of sex hormones. The knowledge about the sympathetic modulation in the secretory phase can explain the symptoms of premenstrual syndrome, which can in turn improve the quality of life among females.