Conditions of autonomic reciprocal interplay versus autonomic co-activation: effects on non-linear heart rate dynamics.
The present study was aimed at investigating the autonomic nervous system influences on the fractal organization of human heart rate during sympathovagal interactions, with special emphasize on the short-term fractal organization in heart rate variability (HRV), as assessed by the scaling exponent (alpha(1)) of the detrended fluctuation analysis. Linear and non-linear HRV analyses were used to study the sympathetic and vagal modulation of heart rate in ten healthy men (mean +/- SEM; age 26 +/- 1 years) during conditions of 1) increased sympathetic activity and vagal withdrawal (head-up tilt), 2) decreased sympathetic activity and increased vagal outflow (thermoneutral upright head-out water immersion, WIn), and 3) simultaneous activation of the two arms of the autonomic nervous activity (upright head-out immersion in cold water, WIc). Hemodynamic and linear HRV results were consistent with previous reports during similar physiological conditions. alpha(1) increased significantly during head-up tilt (from 0.71 +/- 0.13 supine to 0.90 +/- 0.15 upright) and WIn (0.86 +/- 0.10) and was significantly decreased during WIc (0.61 +/- 0.15). Thus, alpha(1) increased when the cardiac autonomic interplay was altered in a reciprocal fashion, whatever the direction of the balance change. Conversely, alpha(1) decreased during the concomitant activation of both vagal and sympathetic activities. The results of linear analysis were necessary to precisely define the direction of change in autonomic control revealed by an increase in alpha(1), while the direction of change in alpha(1) indicated whether an increased vagal activity is coupled with a decreased or increased sympathetic activation. Using both linear and non-linear analysis of HRV may increase the understanding of changes in cardiac autonomic status.
Mourot
Laurent
L
Université de Franche Comté, EA 3920 and IFR133, Physiologie, Faculté de Médecine, Besançon, France. mourotlaurent@hotmail.com
Bouhaddi
Malika
M
Gandelin
Emmanuel
E
Cappelle
Sylvie
S
Nguyen
Nhu Uyen
NU
Wolf
Jean-Pierre
JP
Rouillon
Jean Denis
JD
Hughson
Richard
R
Regnard
Jacques
J
D000328:Adult; D000704:Analysis of Variance; D001127:Arginine Vasopressin / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D001341:Autonomic Nervous System / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D002395:Catecholamines / Q000097:blood; D006257:Head; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D017711:Nonlinear Dynamics; D011187:Posture / Q000502:physiology; D013057:Spectrum Analysis; D014630:Vagus Nerve / Q000502:physiology
D002395:Catecholamines; D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor