Document Detail

Sympathetic restraint of respiratory sinus arrhythmia: implications for vagal-cardiac tone assessment in humans.
MedLine Citation:
PMID:  11356639     Owner:  NLM     Status:  MEDLINE    
Clinicians and experimentalists routinely estimate vagal-cardiac nerve traffic from respiratory sinus arrhythmia. However, evidence suggests that sympathetic mechanisms may also modulate respiratory sinus arrhythmia. Our study examined modulation of respiratory sinus arrhythmia by sympathetic outflow. We measured R-R interval spectral power in 10 volunteers that breathed sequentially at 13 frequencies, from 15 to 3 breaths/min, before and after beta-adrenergic blockade. We fitted changes of respiratory frequency R-R interval spectral power with a damped oscillator model: frequency-dependent oscillations with a resonant frequency, generated by driving forces and modified by damping influences. beta-Adrenergic blockade enhanced respiratory sinus arrhythmia at all frequencies (at some, fourfold). The damped oscillator model fit experimental data well (39 of 40 ramps; r = 0.86 +/- 0.02). beta-Adrenergic blockade increased respiratory sinus arrhythmia by amplifying respiration-related driving forces (P < 0.05), without altering resonant frequency or damping influences. Both spectral power data and the damped oscillator model indicate that cardiac sympathetic outflow markedly reduces heart period oscillations at all frequencies. This challenges the notion that respiratory sinus arrhythmia is mediated simply by vagal-cardiac nerve activity. These results have important implications for clinical and experimental estimation of human vagal cardiac tone.
J A Taylor; C W Myers; J R Halliwill; H Seidel; D L Eckberg
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  280     ISSN:  0363-6135     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2001 Jun 
Date Detail:
Created Date:  2001-05-17     Completed Date:  2001-06-14     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H2804-14     Citation Subset:  IM; S    
Department of Internal Medicine, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Richmond 23249, USA.
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MeSH Terms
Adrenergic beta-Antagonists / pharmacology
Arrhythmia, Sinus / physiopathology,  prevention & control
Biological Clocks / drug effects,  physiology
Blood Pressure / physiology
Carbon Dioxide / metabolism
Fourier Analysis
Heart Catheterization
Heart Rate / drug effects,  physiology*
Models, Cardiovascular*
Muscarinic Antagonists / pharmacology
Reference Values
Reproducibility of Results
Sinoatrial Node / drug effects
Sympathetic Nervous System / drug effects,  physiology*
Tidal Volume / physiology
Tilt-Table Test
Vagus Nerve / physiology*
Grant Support
Reg. No./Substance:
0/Adrenergic beta-Antagonists; 0/Muscarinic Antagonists; 124-38-9/Carbon Dioxide
D L Eckberg / VA Med Ctr, Richmond, VA

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

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