Published Online
on November 8, 2004

A more recent version of this article appeared on November 16, 2004

This Article Full Text (PDF) All Versions of this Article: 110/20/3193    most recent 01.CIR.0000147280.90339.E9v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bonyhay, I. Articles by Freeman, R. Search for Related Content PubMed PubMed Citation Articles by Bonyhay, I. Articles by Freeman, R. Related Collections Autonomic, reflex, and neurohumoral control of circulation

Submitted on February 9, 2004
Revised on May 17, 2004
Accepted on May 20, 2004

Sympathetic Nerve Activity in Response to Hypotensive Stress in the Postural Tachycardia Syndrome

Istvan Bonyhay MD, PhD and Roy Freeman MD^*

From the Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass.

^* To whom correspondence should be addressed. E-mail: rfreeman{at}bidmc.harvard.edu.

Background--Increased central sympathetic activity and/or deficient peripheral sympathetic nerve function are among the proposed pathophysiological changes in patients with the postural tachycardia syndrome (POTS). Little is known about sympathetic nerve outflow and its role in hemodynamic control in this disorder.

Methods and Results--We recorded peroneal muscle sympathetic nerve activity in 9 POTS patients and 9 control subjects at rest and during a nitroprusside-induced hypotensive stimulus. Baseline blood pressure (BP) and heart rate were significantly higher in POTS patients than in controls. At rest, the burst frequency was similar in POTS patients and controls (18.1±6.2 and 20.1±7.9 bursts/min, respectively; P=NS), whereas the burst incidence was significantly lower (23.1±6.8 versus 32.2±11.4 bursts/100 heartbeats, P<0.05). Nitroprusside increased sympathetic outflow significantly more in POTS patients than in controls despite a similar BP decrease (burst frequency 20.4±7.5 versus 12.1±4.1 bursts/min, P=0.008, and burst incidence 21.8±8.4 versus 14.4±5.2 bursts/100 heartbeats, P=0.03). The change in mean burst area, a measure of the number of actively firing sympathetic neurons, was similar in patients and controls (117±15% versus 114±21%, P=NS).

Conclusions--At rest, the tachycardia and normal burst frequency result in normal or even elevated BP in POTS patients. During a hypotensive stimulus, cardiovascular homeostasis is maintained by the increased sympathetic outflow and normal heart rate response despite the lack of concomitant increase in mean burst area that is most likely due to sympathetic denervation.

Key words: nervous system, autonomic • nervous system, sympathetic • blood pressure • tachycardia

This article has been cited by other articles:

				D. S. Goldstein and C. Holmes Neuronal Source of Plasma Dopamine Clin. Chem., November 1, 2008; 54(11): 1864 - 1871. [Abstract] [Full Text] [PDF]

				E. Lambert, N. Eikelis, M. Esler, T. Dawood, M. Schlaich, R. Bayles, F. Socratous, A. Agrotis, G. Jennings, G. Lambert, et al. Altered Sympathetic Nervous Reactivity and Norepinephrine Transporter Expression in Patients With Postural Tachycardia Syndrome Circ Arrhythm Electrophysiol, June 1, 2008; 1(2): 103 - 109. [Abstract] [Full Text] [PDF]

				E. M. Garland, S. R. Raj, B. K. Black, P. A. Harris, and D. Robertson The hemodynamic and neurohumoral phenotype of postural tachycardia syndrome Neurology, August 21, 2007; 69(8): 790 - 798. [Abstract] [Full Text] [PDF]

				J. K. Brooks and L. A.P. Francis Postural orthostatic tachycardia syndrome: Dental treatment considerations J Am Dent Assoc, April 1, 2006; 137(4): 488 - 493. [Abstract] [Full Text] [PDF]

				R. Schondorf, J. Benoit, and R. Stein Cerebral autoregulation is preserved in postural tachycardia syndrome J Appl Physiol, September 1, 2005; 99(3): 828 - 835. [Abstract] [Full Text] [PDF]

				N. Muenter Swift, N. Charkoudian, R. M. Dotson, G. A. Suarez, and P. A. Low Baroreflex control of muscle sympathetic nerve activity in postural orthostatic tachycardia syndrome Am J Physiol Heart Circ Physiol, September 1, 2005; 289(3): H1226 - H1233. [Abstract] [Full Text] [PDF]