Document Detail

Stability of heartbeat interval distributions in chronic high altitude hypoxia.
MedLine Citation:
PMID:  10333977     Owner:  NLM     Status:  MEDLINE    
Recent studies of nonlinear dynamics of the long-term variability of heart rate have identified nontrivial long-range correlations and scale-invariant power-law characteristics (l/f noise) that were remarkably consistent between individuals and were unrelated to external or environmental stimuli (Meyer et al., 1998a). The present analysis of complex nonstationary heartbeat patterns is based on the sequential application of the wavelet transform for elimination of local polynomial nonstationary behavior and an analytic signal approach by use of the Hilbert transform (Cumulative Variation Amplitude Analysis). The effects of chronic high altitude hypoxia on the distributions and scaling functions of cardiac intervals over 24 hr epochs and 4 hr day/nighttime subepochs were determined from serial heartbeat interval time series of digitized 24 hr ambulatory ECGs recorded in 9 healthy subjects (mean age 34 yrs) at sea level and during a sojourn at high altitude (5,050 m) for 34 days (Ev-K2-CNR Pyramid Laboratory, Sagarmatha National Park, Nepal). The results suggest that there exists a hidden, potentially universal, common structure in the heterogeneous time series. A common scaling function with a stable Gamma distribution defines the probability density of the amplitudes of the fluctuations in the heartbeat interval time series of individual subjects. The appropriately rescaled distributions of normal subjects at sea level demonstrated stable Gamma scaling consistent with a single scaled plot (data collapse). Longitudinal assessment of the rescaled distributions of the 24 hr recordings of individual subjects showed that the stability of the distributions was unaffected by the subject's exposure to a hypobaric (hypoxic) environment. The rescaled distributions of 4 hr subepochs showed similar scaling behavior with a stable Gamma distribution indicating that the common structure was unequivocally applicable to both day and night phases and, furthermore, did not undergo systematic changes in response to high altitude. In contrast, a single function stable over a wide range of time scales was not observed in patients with congestive heart failure or patients after cardiac transplantation. The functional form of the scaling in normal subjects would seem to be attributable to the underlying nonlinear dynamics of cardiac control. The results suggest that the observed Gamma scaling of the distributions in healthy subjects constitutes an intrinsic dynamical property of normal heart function that would not undergo early readjustment or late acclimatization to extrinsic environmental physiological stress, e.g., chronic hypoxia.
M Meyer; A Rahmel; C Marconi; B Grassi; P Cerretelli; J E Skinner
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Integrative physiological and behavioral science : the official journal of the Pavlovian Society     Volume:  33     ISSN:  1053-881X     ISO Abbreviation:  Integr Physiol Behav Sci     Publication Date:    1998 Oct-Dec
Date Detail:
Created Date:  1999-07-16     Completed Date:  1999-07-16     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9105843     Medline TA:  Integr Physiol Behav Sci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  344-62     Citation Subset:  IM; S    
Département de Physiologie, CMU, Genève, Switzerland.
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MeSH Terms
Adaptation, Physiological
Altitude Sickness / physiopathology*
Anoxia / physiopathology*
Chronic Disease
Heart Rate / physiology*
Nonlinear Dynamics
Probability Theory
Time Factors
Grant Support

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

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