Document Detail


Influence of respiratory instability during neurocardiogenic presyncope on cerebrovascular and cardiovascular dynamics.
MedLine Citation:
PMID:  17947365     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVE: To analyse the influence of breathing activity on cerebrovascular dynamics during presyncope. DESIGN: Retrospective study. SETTING: University hospital. PATIENTS: 38 subjects developing neurocardiogenic syncope (syncope group), and 61 age-matched control subjects with negative tilt. INTERVENTIONS: Middle cerebral artery mean blood flow velocity (MCFV), continuous non-invasive blood pressure (BP), end-tidal CO(2) (CO(2)-et) and minute ventilation were measured before and during 45' 60 degrees tilting. MAIN OUTCOME MEASURES: Respiratory and cerebrovascular variability, cerebrovascular resistance (CVR)-absolute and corrected for CO(2)-et at 40 mm Hg (CVR-40)-and dynamic cerebrovascular regulation (CVR-dyn: transfer function phase analysis between MCFV and BP), obtained during supine rest (baseline), first 5 minutes of tilt (early tilt), early- and late presyncope (first and second half, respectively, of 4 minutes preceding syncope in syncope group, and equivalent time in controls). RESULTS: Tilting induced a mean (SE) CVR decrease in controls (baseline 1.20 (0.04); late presyncope 1.12 (0.06) mm Hg x s/cm, p<0.05) but not in the syncope group (baseline 1.09 (0.04); late presyncope 1.09 (0.06) mm Hg x s/cm, p = NS). However, CVR-40 showed similar reduction in both groups (controls: from 1.15 (0.04) to 0.96 (0.04) mm Hg x s/cm; syncope group: from 1.01 (0.04) to 0.83 (0.04) mm Hg x s/cm, p = NS). CVR-dyn of the two groups was also similar (p = NS). Respiratory variability increased in the syncope group, from early tilt to late presyncope (p<0.05 or better), preceding hyperventilation and being significantly correlated with an increase in MCFV and BP variability (p<0.01). CONCLUSIONS: During presyncope, the development of respiratory instability and hypocapnia impairs MCFV, thus facilitating the onset of syncope despite preserved cerebrovascular regulation.
Authors:
C Porta; G Casucci; S Castoldi; A Rinaldi; L Bernardi
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Publication Detail:
Type:  Journal Article     Date:  2007-10-18
Journal Detail:
Title:  Heart (British Cardiac Society)     Volume:  94     ISSN:  1468-201X     ISO Abbreviation:  Heart     Publication Date:  2008 Nov 
Date Detail:
Created Date:  2008-10-20     Completed Date:  2008-12-10     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9602087     Medline TA:  Heart     Country:  England    
Other Details:
Languages:  eng     Pagination:  1433-9     Citation Subset:  AIM; IM    
Affiliation:
Department of Internal Medicine, University of Pavia and IRCCS Ospedale S Matteo, Pavia, Italy.
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MeSH Terms
Descriptor/Qualifier:
Adult
Blood Pressure / physiology*
Carbon Dioxide / physiology
Cardiovascular System / physiopathology*
Cerebrovascular Circulation / physiology
Female
Hemodynamics / physiology
Humans
Hypocapnia / complications,  physiopathology*
Male
Oxygen Consumption / physiology
Retrospective Studies
Syncope / complications,  physiopathology*
Syncope, Vasovagal / complications,  physiopathology
Tilt-Table Test / methods
Chemical
Reg. No./Substance:
124-38-9/Carbon Dioxide
Comments/Corrections
Comment In:
Heart. 2008 Nov;94(11):1372-3   [PMID:  18931152 ]

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


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