Quantitative beat-to-beat analysis of heart rate dynamics during
exercise.
Tulppo, Mikko P., Timo H. M[umlaut]akikallio, Timo E. S. Takala, Tapio
Sepp[umlaut]anen, and Heikki V. Huikuri.
Merikoski Rehabilitation and Research Center (M. P. T., T. H. M.),
Oulu, Finland, Division of Cardiology (T. H. M, T. S., H. V. H.),
Dept. of Medicine, University of Oulu, Oulu, Finland and Dept. of
Biology of Physical Activity (M. P. T., T. E. S. T.), University of
Jyv[umlaut]askyl[umlaut]a, Jyv[umlaut]askyl[umlaut]a, Finland
APStracts 3:0028H, 1996.
Beat-to-beat heart rate dynamics were studied by plotting each R-R
interval as a function of the previous R-R interval (Poincar[acute]e
plot) during incremental doses of atropine followed by exercise for
10 subjects and during exercise without autonomic blockade for 31
subjects. A quantitative two dimensional vector analysis of a
Poincar[acute]e plot was used by measuring separately the standard
deviation of instantaneous beat-to-beat R-R interval variability
(SD1) and the standard deviation of continuous, long-term R-R
interval variability (SD2) as well as the SD1/SD2 ratio. The
quantitative Poincar[acute]e measures were compared with linear
measures of HRV and with approximate entropy (ApEn), both at rest and
during exercise. A linear progressive reduction was observed in SD1
during atropine administration and it remained almost at the zero
level during the exercise after a parasympathetic blockade. Atropine
resulted in more variable changes in SD2 and the SD1/SD2 ratio, but
during the exercise after the parasympathetic blockade a progressive
increase was observed in the SD1/SD2 ratio until the end of the
exercise. The SD1/SD2 ratio had no significant correlations with the
frequency domain measures of HRV. However, the SD1/SD2 ratio had a
modest correlation with ApEn at rest (r = -0.69, p < 0.001), but
not during the exercise (r = 0.27, ns). All measures of vagal
modulation of HR decreased progressively until the ventilatory
threshold level was reached, whereafter sympathetic activation was
reflected as changes in the SD1/SD2 ratio. These results show that
the quantitative two dimensional vector analysis of a Poincar[acute]e
plot can provide useful information on the vagal modulation of R-R
interval dynamics during exercise, which are not easily detected by
linear summary measures of HRV or by ApEn.
Received 18 July 1995; accepted in final form 2 January 1996.
APS Manuscript Number H676-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96