Document Detail

Mechanisms underlying very-low-frequency RR-interval oscillations in humans.
MedLine Citation:
PMID:  9714112     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Survival of post-myocardial infarction patients is related inversely to their levels of very-low-frequency (0.003 to 0.03 Hz) RR-interval variability. The physiological basis for such oscillations is unclear. In our study, we used blocking drugs to evaluate potential contributions of sympathetic and vagal mechanisms and the renin-angiotensin-aldosterone system to very-low-frequency RR-interval variability in 10 young healthy subjects. METHODS AND RESULTS: We recorded RR intervals and arterial pressures during three separate sessions, with the patient in supine and 40 degree upright tilt positions, during 20-minute frequency (0.25 Hz) and tidal volume-controlled breathing after intravenous injections: saline (control), atenolol (0.2 mg/kg, beta-adrenergic blockade), atropine sulfate (0.04 mg/kg, parasympathetic blockade), atenolol and atropine (complete autonomic blockade), and enalaprilat (0.02 mg/kg, ACE blockade). We integrated fast Fourier transform RR-interval spectral power at very low (0.003 to 0.03 Hz), low (0.05 to 0. 15 Hz), and respiratory (0.2 to 0.3 Hz) frequencies. Beta-adrenergic blockade had no significant effect on very-low- or low-frequency RR-interval power but increased respiratory frequency power 2-fold. ACE blockade had no significant effect on low or respiratory frequency RR-interval power but modestly (approximately 21%) increased very-low-frequency power in the supine (but not upright tilt) position (P<0.05). The most profound effects were exerted by parasympathetic blockade: Atropine, given alone or with atenolol, abolished nearly all RR-interval variability and decreased very-low-frequency variability by 92%. CONCLUSIONS: Although very-low-frequency heart period rhythms are influenced by the renin-angiotensin-aldosterone system, as low and respiratory frequency RR-interval rhythms, they depend primarily on the presence of parasympathetic outflow. Therefore the prognostic value of very-low-frequency heart period oscillations may derive from the fundamental importance of parasympathetic mechanisms in cardiovascular health.
J A Taylor; D L Carr; C W Myers; D L Eckberg
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation     Volume:  98     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1998 Aug 
Date Detail:
Created Date:  1998-09-15     Completed Date:  1998-09-15     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  547-55     Citation Subset:  AIM; IM; S    
Department of Internal Medicine, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, and Medical College of Virginia, Virginia Commonwealth University, Richmond, USA.
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MeSH Terms
Angiotensin-Converting Enzyme Inhibitors / pharmacology
Blood Pressure / drug effects,  physiology
Head-Down Tilt
Heart Rate / drug effects,  physiology*
Parasympatholytics / pharmacology
Respiration / drug effects,  physiology
Supine Position
Tidal Volume
Grant Support
Reg. No./Substance:
0/Angiotensin-Converting Enzyme Inhibitors; 0/Parasympatholytics
D L Eckberg / Med Coll VA, Richmond

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

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