A simple model for the simulation of low frequency heart rate variability waves

The purpose of this study was mathematical modeling of the low frequency heart rate variability wave (LFHR) and its response to isoproterenol (ISP) infusion. In a previous study the authors found that the steady-state HR can be described as a hyperbolic power function of the steady-state ISP flow rate. This dependency was coupled with a first order difference equation to form a pharmacodynamic model that reliably describes the relationship between filtered HR and ISP flow for any arbitrary form of ISP flow function. In the authors´ present study they used the filtered-HR-ISP model as part of a proportional integral derivative control loop and showed that this new simple model can simulate LFHR waves. When using filtered and smoothed HR from the experiments as dynamic set-point for the controller the authors found high correlation between LFHR amplitude (R=0.9) and frequency (R=0.87) of the model and the experimental results. This new model can be used for better understanding of the dynamic properties of LFHR waves. It may also be used as a wave generator for testing new methods for the appreciation of LFHR waves.