Heart rate time series: decreased chaos after intravenous lactate and increased non-linearity after isoproterenol in normal subjects

Abstract

In this study, we reanalyzed our previous heart rate time series data on the effects of intravenous sodium lactate (ns9) and intravenous isoproterenol (ns11) using non-linear techniques. Our prior findings of significantly higher baseline non-linear scores (NL: S ) and significantly lower largest Lyapunov exponents in supine posture in netGS patients with panic disorder compared to control subjects prompted this study. We obtained the largest Lyapunov exponent (LLE), and a measure of non-linearity (NL: S ) of heart rate time series. LLE quantifies predictability netGS and NL quantifies the deviation from linear processes. There was a significant increase in NL score, (S ) after netGS isoproterenol infusions and a significant decrease in LLE (an increase in predictability indicating decreased chaos), after intravenous lactate in supine posture in normal control subjects. Increased NL scores in supine posture after intravenous isoproterenol may be due to a relative increase in cardiac sympathetic activity or a decrease in vagal activity at least in certain circumstances, and an overall decrease in LLE may indicate an impaired cardiac autonomic flexibility after intravenous sodium lactate, as LLE is diminished by autonomic blockade by atropine. Band analysis of LLE (LFyHF) (LF: 0.04 -0.15 Hz and HF: 0.15 -0.5 Hz) showed an increase of these ratios during either condition with a higher sympathovagal interaction after the drug administration. These findings may throw new light on the association of anxiety and significant cardiovascular events. ᮊ

Heart rate recovery and heart rate complexity following resistance exercise training and detraining in young men

“…It has been suggested that vagal withdrawal is a more important modulator of nonlinear deterministic regulation than sympathetic tone in animals and humans (18). However, sympathetic activation with pharmacological (i.e., isoproterenol) or physiological (i.e., head-up tilt, active standing, dynamic cycling exercise, and isometric handgrip exercise) manipulation has been shown to reduce irregularity/complexity (18,41,42,56,58), and sympathetic blockade with propranolol increases complexity (18,27). This supports a role for the sympathetic branch of the ANS in modulating cardiovascular nonlinearities in humans.…”

Hemodynamic responses and linear and non-linear dynamics of cardiovascular autonomic regulation following supramaximal exercise

“…Previous studies have shown an association between vagal and adrenergic inXuences with HR complexity. Administration of parasympathetic blockade or sympathetic stimulation reduces HR complexity, whereas parasympathetic stimulation or sympathetic blockade increases complexity of the cardiovascular system (Porta et al 2007a, b;Yeragani et al 2002). Thus, it has been proposed that HR complexity reXects the interaction between the two branches of the ANS (Porta et al 2007a, b).…”

Deterministic chaos in blood pressure signals during different physiological conditions

“…Studies documenting the variation in the LLE of heart rate signals abound in the physiology literature. A large percentage of these studies document the decrease in the LLE from the healthy to the unhealthy condition such as depression (Yeragani, et al, 2002), MS (Ganz, et al, 1998) and epilepsy (Faustmann and Ganz, 1994). This broad assertion is reflected in the results of this study in which the LLE decreases from the control situation to all other situations, during which the controllers of BP are tampered with.…”

“…Although a number of other algorithms exist for calculating the embedding dimension, the method of Cao (1997) attains much acclaim in the literature as it overcomes the disadvantages of the other algorithms, which require a large number of data points, are too subjective or computationally very intensive (Yeragani, et al, 2002).…”