Effects of cardiovascular parameter changes on heart rate variability: analysis by a mathematical model of short-term...

A mathematical model of short-term cardiovascular regulation is used to investigate how heart period power spectrum reflects alterations in cardiovascular parameters. The model includes the pulsating heart, the systemic and pulmonary circulation, the mechanical effects of respiration on hemodynamics, two groups of receptors (arterial baroreceptors and lung-stretch receptors), the sympathetic and vagal efferent branches, several distinct effectors, and a very low frequency vasomotor noise. All parameters in the model are assigned on the basis of the physiological literature. With basal parameter values, the simulated heart period (HP) power spectrum exhibits a high frequency (HF) peak, synchronous with respiration (0.2 Hz) and a smaller low frequency (LF) component around 0.1 Hz. Model results stress that the features of the HP spectrum are influenced by several factors, other than strength and integrity of autonomic nervous system. In particular, sensitivity analyses reveal that alterations in total peripheral resistance and in left ventricle contractility affect HP spectrum markedly, by causing a change in the working point of the autonomic control mechanisms. The model may be useful in the physiopathological interpretation of heart rate variability, to relate changes in HP spectrum with autonomic and/or cardiovascular perturbations.