Document Detail

Dysfunctional baroreflex regulation of sympathetic nerve activity in patients with vasovagal syncope.
MedLine Citation:
PMID:  12668496     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The interplay of resting muscle sympathetic nerve activity (MSA) and the baroreceptor reflex in patients with vasovagal syncope remains elusive. Hence, the aim of the present study was to investigate MSA, baroreceptor sensitivity, heart rate, and blood pressure under resting conditions and during orthostatic stress in patients with a history of vasovagal syncope. METHODS AND RESULTS: MSA was measured using microneurography at rest and during lower body negative pressure (LBNP) to mimic orthostatic stress in patients with a history of vasovagal syncope (n=10) and in age-matched healthy controls (n=8). Heart rate and blood pressure were simultaneously recorded. Cardiac baroreceptor sensitivity was calculated with the spectral technique (alpha coefficient). Resting MSA in the patients with syncope was significantly increased as compared with controls (42.4+/-2.3 versus 26.5+/-3.6 bursts/min, P=0.001), whereas activation of MSA during orthostatic stress in the patient group was significantly blunted (5.1+/-1.6 versus 15.2+/-2.1 bursts/min at LBNP -50 mm Hg, P=0.002). In the patients with syncope, cardiac baroreceptor sensitivity was significantly reduced under supine resting conditions (8.5+/-0.7 versus 13.0+/-1.1 ms/mm Hg, P=0.001), as well as under orthostatic stress (7.3+/-0.7 versus 13.4+/-1.5 ms/mm Hg, P=0.003). CONCLUSIONS: This study shows that in patients with vasovagal syncope, resting MSA is increased and baroreflex regulation during orthostatic stress is blunted, thus leading to impaired MSA adaptation. These results provide new insights into mechanisms of vasovagal syncope and suggest that pharmacological modulation of baroreceptor sensitivity may represent a promising treatment of neuromediated syncope.
Markus Béchir; Christian Binggeli; Roberto Corti; Rémy Chenevard; Lukas Spieker; Frank Ruschitzka; Thomas F Lüscher; Georg Noll
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2003-02-24
Journal Detail:
Title:  Circulation     Volume:  107     ISSN:  1524-4539     ISO Abbreviation:  Circulation     Publication Date:  2003 Apr 
Date Detail:
Created Date:  2003-04-01     Completed Date:  2003-04-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1620-5     Citation Subset:  AIM; IM; S    
Cardiovascular Center, Cardiology, University Hospital, Rämistrasse 100, 8091 Zürich, Switzerland.
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MeSH Terms
Baroreflex / physiology*
Blood Pressure
Heart / innervation,  physiopathology
Heart Rate
Lower Body Negative Pressure / adverse effects
Muscles / innervation
Pressoreceptors / physiopathology
Sympathetic Nervous System / physiopathology*
Syncope, Vasovagal / diagnosis,  etiology,  physiopathology*
Comment In:
Circulation. 2004 Mar 30;109(12):e171; author reply e171   [PMID:  15051654 ]

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

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