Document Detail

Disruption of phase synchronization between blood pressure and muscle sympathetic nerve activity in postural vasovagal syncope.
MedLine Citation:
PMID:  23934851     Owner:  NLM     Status:  MEDLINE    
Withdrawal of muscle sympathetic nerve activity (MSNA) may not be necessary for the precipitous fall of peripheral arterial resistance and arterial pressure (AP) during vasovagal syncope (VVS). We tested the hypothesis that the MSNA-AP baroreflex entrainment is disrupted before VVS regardless of MSNA withdrawal using the phase synchronization between blood pressure and MSNA during head-up tilt (HUT) to measure reflex coupling. We studied eight VVS subjects and eight healthy control subjects. Heart rate, AP, and MSNA were measured during supine baseline and at early, mid, late, and syncope stages of HUT. Phase synchronization indexes, measuring time-dependent differences between MSNA and AP phases, were computed. Directionality indexes, indicating the influence of AP on MSNA (neural arc) and MSNA on AP (peripheral arc), were computed. Heart rate was greater in VVS compared with control subjects during early, mid, and late stages of HUT and significantly declined at syncope (P = 0.04). AP significantly decreased during mid, late, and syncope stages of tilt in VVS subjects only (P = 0.001). MSNA was not significantly different between groups during HUT (P = 0.700). However, the phase synchronization index significantly decreased during mid and late stages in VVS subjects but not in control subjects (P < .001). In addition, the neural arc was significantly affected more than the peripheral arc before syncope. In conclusion, VVS is accompanied by a loss of the synchronous AP-MSNA relationship with or without a loss in MSNA at faint. This provides insight into the mechanisms behind the loss of vasoconstriction and drop in AP independent of MSNA at the time of vasovagal faint.
Christopher E Schwartz; Elisabeth Lambert; Marvin S Medow; Julian M Stewart
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2013-08-09
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  305     ISSN:  1522-1539     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2013 Oct 
Date Detail:
Created Date:  2013-10-16     Completed Date:  2013-12-06     Revised Date:  2014-10-15    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H1238-45     Citation Subset:  IM    
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MeSH Terms
Baroreflex / physiology*
Blood Pressure / physiology*
Case-Control Studies
Heart Rate / physiology*
Peroneal Nerve / physiology,  physiopathology*
Postural Orthostatic Tachycardia Syndrome / complications
Retrospective Studies
Sympathetic Nervous System / physiology,  physiopathology*
Syncope, Vasovagal / complications,  physiopathology*
Tilt-Table Test
Young Adult
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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