Effects of oral contraceptives on sympathetic baroreflex sensitivity during Valsalva's maneuver

Abstract

A recent study reported increased cardiovagal baroreflex sensitivity (BRS) in women taking oral contraceptives (OC) compared to naturally eumenorrheic women (EW) during low hormone phases of the menstrual cycle (OC placebo vs. early follicular), but sympathetic BRS was not reported. We hypothesized an increased sympathetic BRS in OC compared to EW. Muscle sympathetic nerve activity (MSNA), arterial pressure (systolic: SAP, diastolic: DAP), and heart rate were recorded during three Valsalva maneuvers in 23 healthy females (12 EW, 11 OC) during the low hormone phase of the menstrual cycle. Resting MSNA, arterial pressure, and heart rate were not different between groups. The phase II SAP decrease was exaggerated in the OC users (OC: 32 ± 4 mmHG vs. EW: 20 ± 2 mmHG; p < 0.05), but phase II MSNA and sympathetic BRS (%Total MSNA/ΔDAP) did not differ between groups. The rise in SAP (OC: 35 ± 5 mmHG vs. EW: 18 ± 2 mmHG; p < 0.05) and DAP (OC: 18 ± 3 mmHG vs. EW: 10 ± 1 mmHG; p < 0.05) during phase IV were also augmented in the OC group, but the cardiovagal BRS (slope of R‐R interval and SAP) was not different between OC and EW. In conclusion, our results indicate cardiovagal and sympathetic BRS in women taking oral contraceptives are similar to naturally menstruating women during the low hormone phase of the menstrual cycle. However, oral contraceptives appear to exaggerate arterial pressure changes during Valsalva's maneuver. Supported by NIH (HL‐088689).