Document Detail

Origins of heart rate variability: relationship of heart rate burst morphology to work duration and load.
MedLine Citation:
PMID:  10516187     Owner:  NLM     Status:  MEDLINE    
We are developing a lexicon of specific heart period changes, or lexons, that recur frequently and whose physiological meaning can be read into ambulatory electrocardiogram (ECG). The transient, reversible "burst" of tachycardia induced by exercise initiation can also be seen on ambulatory ECG. We hypothesized that burst morphology depended on the work that preceded it and on baroreceptor activation. Ten subjects with mean age 38 yr (range 17-69 yr) underwent two protocols of semisupine cycling in which load and duration were varied. Burst duration increased with longer cycling times (median values of 18.0, 25.5, and 23.7 s with 1, 3, and 5 s of cycling, respectively; P = 0.033). Burst shape as assessed by heart period exponential decay constant and burst magnitude did not change. To assess the impact of workload, subjects cycled for 5 s at loads of 0, 25, 50, and 75 W. No significant differences were seen in burst duration, burst magnitude, or burst shape. Tachycardia preceded hypotension by 4.6 +/- 2.2 s, which is inconsistent with baroreceptor involvement in the onset of burst tachycardia. Because burst morphology is a nearly quantal response to the initiation of exercise, the presence of a burst on an ambulatory ECG implies the onset of exercise.
D Roach; R Haennel; M L Koshman; R Sheldon
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  277     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1999 Oct 
Date Detail:
Created Date:  1999-11-17     Completed Date:  1999-11-17     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H1491-7     Citation Subset:  IM; S    
Cardiovascular Research Group, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
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MeSH Terms
Blood Pressure / physiology
Electrocardiography, Ambulatory
Heart Rate / physiology*
Middle Aged
Physical Exertion / physiology*
Supine Position
Time Factors

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

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