Session P83.2

Positive Correlation between Heart Rate Variability and Stochastic Nervous Modulation: A Computer Simulation Study

H Zhang*, AV Holden

The University of Manchester
Manchester, UK

The normal heart rhythm is generated and controlled by the pacemaker of the heart, the sinoatrial node (SAN), which consists of ~104 pacemaking cells. The endogenous rhythmicity of single SAN cells emerges from integrated actions of over a dozen types of membrane ion channels, each of which consists of ~106 single ion channels. In normal conditions, the in vivo cardiac rhythm is irregular with heart rate varies from time to time. Heart rate variation (HRV) is clinically relevant, and indicative of a pathology. However, the mechanisms underlying the HRV are still controversial and stochastic nervous modulation has been hypothesized as one of the major responsible factors. Though previous experimental studies have implicated possible involvements of autonomic nervous modulation and the HRV, there is no explicit data yet providing a causative link between the two. To elucidate a possible correlation between HRV and stochastic nerve activity, in this study a biophysically detailed mathematical model of the electrical action potentials of rabbit sinoatrial node (SA) was implement to study the concentration-dependent effects of acetylcholine (ACh), a neurotransmitter released by parasympathetic neurons, on the pacemaker activity of the heart and the HRV. By considering the stochastic activity of parasympathetic nerve system, i.e., randomly fluctuating ACh concentration produces varying rate of depolarization during the pacemaker potential leading to varied cycle length (CL) of spontaneous action potentials. Consequently irregular behavior of HRV can be shown by fluctuating CL that presents chaotic characteristics with a positive Lyapunov exponent although the underlying process is stochastic. A positive correlation between the measured time series of CL and ACh has also been revealed. This study provides a solid evidence to support the hypothesis that stochastic nervous modulation is associated with the HRV, which may be produced by a deterministic system driven by a stochastic process, even though it can show chaotic characteristics.

(Abstract Control Number: 89)