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

Hart, Emma C. PhD1; Charkoudian, Nisha PhD2; Joyner, Michael J. MD1; Barnes, Jill N. PhD1; Curry, Timothy B. MD, PhD1; Casey, Darren P. PhD1

doi: 10.1097/GME.0b013e3182843b59
Original Articles

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.

From the 1Department of Anesthesiology, Mayo Clinic, Rochester, MN; and 2Thermal and Mountain Medicine Division, The US Army Research Institute of Environmental Medicine, Natick, MA.

Received August 31, 2012; revised and accepted December 20, 2012.

Dr. Casey is currently affiliated with the Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, Iowa City, IA.

Funding/support: This study was supported by National Institutes of Health grants HL083947 (M.J.J. and N.C.), AR55819 (D.P.C.), AG038067 (J.N.B.), and AHA 070036Z (E.C.H.), and by National Center for Research Resources grant 1 UL1 RR024150. Additional support was received from the Mayo Foundation, including a philanthropic gift from the Caywood family and the Mayo Clinic Department of Anesthesia.

Financial disclosure/conflicts of interest: None reported.

The content of this work is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.

Address correspondence to: Darren P. Casey, PhD, Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, IA 52242. E-mail: darren-casey@uiowa.edu

© 2013 by The North American Menopause Society.