Cardiovascular and cerebrovascular responses to head-up-tilt throughout the normal menstrual cycle

Date

2012

Authors

Wu, Yi-Chiann

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Abstract

Orthostatic tolerance depends on maintenance of cerebral blood flow. Gender differences in orthostatic tolerance may suggest influences of ovarian hormones on cerebral blood flow. PURPOSE: To test the hypothesis that cerebral blood velocity is decreased during upright tilt when ovarian hormones are increased during the normal menstrual cycle. METHODS: Ten healthy, eumenorrheic female subjects (age 26 +/- 1.4yrs, height 167 +/- 3.3 cm, and weight 66 +/- 2.3 kg; mean +/- SE) rested quietly for ten minutes in the supine position, and were then tilted upright (HUT) to 70° for another ten minutes on four occasions, during the four different phases of the menstrual cycle: Early Follicular (Days 1-2; EF), Late Follicular (Days 12-13; LF), Early Luteal (Days 16-17; EL), and Late Luteal (Days 26-27; LL). Estrogen and progesterone concentrations were analyzed from blood. ECG, beat-by-beat finger arterial pressures, end-tidal CO2, and cerebral blood velocity were recorded during the last five minutes of supine and during the last five minutes of HUT. RESULTS: Estrogen was significantly higher during the late follicular phase (P = .004) and progesterone was significant higher during the early luteal phase (P = .002). The results indicated no significant differences between the four phases of menstrual cycle for heart rate, blood pressure (systolic; SAP diastolic; DAP, and mean; MAP), stroke volume, cardiac output, or cerebral blood velocities (systolic (MCAvS), diastolic (MCAsD) and mean (MCAsM)) in either the supine or HUT positions. However, MCAvS was lowest in HUT during EL compared with supine LL (interaction P = 0.06). CONCLUSIONS: Cardiovascular and cerebrovascular responses to HUT are not influenced by fluctuating ovarian hormones throughout the normal menstrual cycle. The tendency for MCAvS to be lower during HUT when ovarian hormones are higher may be clinically relevant.

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Keywords

Estrogen, Menstrual cycle, Orthostatic intolerance, Orthostatic tolerance, Ovarian hormones

Citation

Department

Health and Kinesiology