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Beat-to-beat heart rate (HR) dynamics were studied by plotting each R-R interval as a function of the previous R-R interval (Poincaré 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 Poincaré plot was used by(More)
This study was designed to assess the effects of age and physical fitness on vagal modulation of heart rate (HR) during exercise by analyzing the instantaneous R-R interval variability from Poincaré plots (SD1) at rest and at different phases of a bicycle exercise test in a population of healthy males. SD1 normalized for the average R-R interval (SD1n), a(More)
An experimental comparison of shape classification methods based on autoregressive modeling and Fourier descriptors of closed contours is carried out. The performance is evaluated using two independent sets of data: images of letters and airplanes. Silhouette contours are extracted from non-occluded 2-D objects rotated, scaled and translated in 3-D space.(More)
BACKGROUND Beat-to-beat analysis of RR intervals can reveal patterns of heart-rate dynamics, which are not easily detected by summary measures of heart-rate variability. This study was designed to test the hypothesis that alterations in RR-interval dynamics occur before the spontaneous onset of ventricular tachyarrhythmias (VT). METHODS AND RESULTS(More)
tk;1Passive head-up tilt and exercise result in specific changes in the spectral characteristics of heart rate (HR) variability as a result of reduced vagal and enhanced sympathetic outflow. Recently analytic methods based on nonlinear system theory have been developed to characterize the nonlinear features in HR dynamics. This study was designed to assess(More)
Concomitant sympathetic and vagal activation can occur in various physiological conditions, but there is limited information on heart rate (HR) behavior during the accentuated sympathovagal antagonism. Beat-to-beat HR and blood pressure were recorded during intravenous infusion of incremental doses of norepinephrine in 18 healthy male volunteers (mean age(More)
BACKGROUND Altered fractal heart rate (HR) dynamics occur during various disease states, but the physiological background of abnormal fractal HR behavior is not well known. We tested the hypothesis that the fractal organization of human HR dynamics is determined by the balance between sympathetic and vagal outflow. METHODS AND RESULTS A short-term fractal(More)
BACKGROUND The prognostic role of heart rate (HR) variability analyzed from 24-hour ECG recordings in the general population is not well known. We studied whether analysis of 24-hour HR behavior is able to predict mortality in a random population of elderly subjects. METHODS AND RESULTS A random sample of 347 subjects of > or =65 years of age (mean,(More)