Relationship between sympathetic nerve activity and aortic wave reflection characteristics in postmenopausal women

OBJECTIVE: Aortic wave reflection characteristics, such as augmentation index, are positively related to muscle sympathetic nerve activity in young men. In young women, there is an inverse relationship. We investigated whether this inverse relationship persisted in postmenopausal women.

METHODS: Muscle sympathetic nerve activity (peroneal microneurography) and arterial pressure (brachial catheter) were measured in 16 postmenopausal women (mean [SEM] age, 60 [2] y). Aortic blood pressure and wave form characteristics were synthesized from radial arterial pressure waves (applanation tonometry). Specifically, augmentation index, wave reflection amplitude, and estimated wasted left ventricular energy were calculated. These data were compared with our previously published work from an identical protocol in 23 young women (mean [SEM] age, 25 [1] y).

RESULTS: Tonic sympathetic activity was higher in postmenopausal women than in young women (64 [3] vs 24 [4] bursts/100 heartbeats). All indices of aortic wave reflection were higher in postmenopausal women than in young women (P < 0.05). Baseline sympathetic activity was inversely related to augmentation index (r = -0.63, P < 0.05), augmented pressure (r = -0.62, P < 0.05), and wasted left ventricular energy (r = -0.61, P < 0.05) in young women. Conversely, baseline sympathetic activity was positively related to augmentation index (r = 0.63, P = 0.09), augmented pressure (r = 0.69, P < 0.05), and wasted left ventricular energy (r = 0.79, P < 0.05) in postmenopausal women.

CONCLUSIONS: High levels of sympathetic activity are associated with higher indices of aortic wave reflection in postmenopausal women. Consequently, postmenopausal women with high sympathetic activity may be more at risk for developing cardiovascular diseases or experiencing adverse cardiovascular system-related events.