Quantitative evaluation of heart rate variability associated with autonomic nervous system dysfunction/blockade

In this study we performed a quantitative evaluation of the Heart Rate Variability (HRV) associated with normals and in patients with Autonomous Nervous System (ANS) dysfunction of two different origins: diabetic neuropathy and pharmacologically induced ANS blockade (after atropine and propanolol administration). Simple time and frequency domain statistics were computed from the RR time series. Due to of the strong evidence of nonlinearity in the cardiovascular system, the linear approach was extended by computing the correlation dimension (CD) as an estimator of the complexity of the three categories of data. The potential discriminating character of CD was examined as well as the validity of this estimator. We found that in the case of drug induced ANS blockade CD was statistically significantly less than in the other cases (normal and pathological ANS blockade). However, analysis of surrogate applied on the three categories of patients failed to assign nonlinear properties as captured by CD, suggesting that linear correlation is also involved.