Sympathetic neural activity, sex dimorphism, and postural tachycardia syndrome
Article first published online: 14 MAR 2007
Copyright © 2007 American Neurological Association
Annals of Neurology
Volume 61, Issue 4, pages 332–339, April 2007
How to Cite
Bonyhay, I. and Freeman, R. (2007), Sympathetic neural activity, sex dimorphism, and postural tachycardia syndrome. Ann Neurol., 61: 332–339. doi: 10.1002/ana.21090
- Issue published online: 24 APR 2007
- Article first published online: 14 MAR 2007
- Manuscript Revised: 12 DEC 2007
- Manuscript Received: 12 SEP 2007
- Manuscript Accepted: 5 JAN 2007
- NIH (National Heart, Lung, and Blood Institute). Grant Number: 1 R01 HL 59459
- Beth Israel Deaconess Medical General Clinical Research Center. Grant Number: M01-RR01032
To elucidate the mechanisms whereby postural tachycardia syndrome (POTS) patients maintain orthostatic blood pressure and explain the greater prevalence of female cases in POTS cohorts.
We investigated muscle sympathetic nerve (MSN) discharge characteristics in 12 female POTS patients and in 9 male and 12 female control subjects using the burst amplitude distribution and the relative contribution of burst frequency and burst amplitude.
At rest, burst distribution was shifted toward larger amplitudes in POTS patients (p < 0.005), consistent with increased sympathetic activity. During hypotension, the distribution shifted toward larger amplitude bursts in control subjects (p < 0.001), whereas it did not change in POTS patients. Total MSN activity increase to hypotension did not differ between subject groups, but the relative contribution of burst frequency change to the total activity increase was greater in POTS patients than in female (p < 0.05) and male (p < 0.001) control subjects. In contrast, the relative contribution of burst amplitude change to total MSN activity increase was greater in male compared with female control subjects (p < 0.05) and POTS patients (p < 0.001).
At rest, the burst amplitude distribution was consistent with increased sympathetic activity in POTS and did not change in response to hypotension. In response to hypotension, burst frequency makes a proportionally greater contribution to the increase in total MSN activity in POTS patients compared with female control subjects, and female compared with male control subjects. These physiological differences in MSN discharge characteristics, in the setting of sympathetic fiber loss associated with POTS, may contribute to the predisposition to and greater prevalence of POTS in female individuals. Ann Neurol 2007