Periovulatory Subphase of the Menstrual Cycle Is Marked by a Significant Decrease in Heart Rate Variability.

Area of Science:

• Physiology
• Cardiovascular Health
• Reproductive Endocrinology

Background:

• High-frequency heart rate variability (HF-HRV) is a key ultradian rhythm reflecting parasympathetic nervous system (PNS) activity.
• The variation of HF-HRV across the menstrual cycle (MC) and potential mediation by progesterone remain largely unexplored.
• Understanding these fluctuations is crucial given women's higher cardiovascular disease mortality rates.

Purpose of the Study:

• To investigate how HF-HRV changes throughout the menstrual cycle.
• To determine if progesterone levels correlate with HF-HRV variations across different menstrual cycle phases.
• To identify specific menstrual cycle phases associated with significant HF-HRV alterations.

Main Methods:

• Recruited 33 women for eight clinic visits across their MC.
• Measured resting HF-HRV and collected serum samples for luteinizing hormone (LH) and progesterone analysis.
• Realigned data to LH surge, defining early follicular, mid-follicular, periovulatory, early luteal, mid-luteal, and late luteal subphases.

Main Results:

• Significant differences in HF-HRV were observed between the early follicular and periovulatory phases (p ≤ 0.001).
• A significant drop in HF-HRV was noted between the periovulatory and early luteal phases (p ≤ 0.05).
• Progesterone showed a positive association with HF-HRV during the early follicular phase, but not the periovulatory phase (p ≤ 0.05).

Conclusions:

• HF-HRV experiences a notable decrease in anticipation of ovulation.
• Progesterone's association with HF-HRV differs across menstrual cycle phases.
• Further research is essential to understand these HF-HRV dynamics in women, particularly concerning cardiovascular health.