Baroreflex control of muscle sympathetic nerve activity in postural orthostatic tachycardia syndrome

N. Muenter Swift, N. Charkoudian, R. M. Dotson, G. A. Suarez, P. A. Low

Research output: Contribution to journalArticle

41 Scopus citations

Abstract

Postural orthostatic tachycardia syndrome (POTS) is characterized by excessive tachycardia during orthostasis. To test the hypothesis that patients with POTS have decreased sympathetic neural responses to baroreflex stimuli, we measured heart rate (HR) and muscle sympathetic nerve activity (MSNA) responses to three baroreflex stimuli including vasoactive drug boluses (modified Oxford technique), Valsalva maneuver, and head-up tilt (HUT) in POTS patients and healthy control subjects. The MSNA response to the Valsalva maneuver was significantly greater in the POTS group (controls, 26 ± 7 vs. POTS, 48 ± 6% of baseline MSNA/mmHg; P = 0.03). POTS patients also had an exaggerated MSNA response to 30° HUT (controls, 123 ± 24 vs. POTS, 208 ± 30% of baseline MSNA; P = 0.03) and tended to have an exaggerated response to 45° HUT (controls, 137 ± 27 vs. POTS, 248 ± 58% of baseline MSNA; P = 0.10). Sympathetic baroreflex sensitivity calculated during administration of the vasoactive drug boluses also tended to be greater in the POTS patients; however, this did not reach statistical significance (P = 0.15). Baseline MSNA values during supine rest were not different between the groups (controls, 23 ± 4 vs. POTS, 16 ± 5 bursts/100 heartbeats; P = 0.30); however, resting HR was significantly higher in the POTS group (controls, 58 ± 3 vs. POTS, 82 ± 4 beats/min; P = 0.0001). Our results suggest that POTS patients have exaggerated MSNA responses to baroreflex challenges compared with healthy control subjects, although resting supine MSNA values did not differ between the groups.

Original languageEnglish (US)
Pages (from-to)H1226-H1233
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume289
Issue number3 58-3
DOIs
StatePublished - Sep 1 2005

Keywords

  • Blood pressure
  • Head-up tilt
  • Heart rate
  • Intolerance
  • Valsalva maneuver

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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