Comparing the Fidelity of Atrioventricular Dynamics for Varying Heart Rate in Different Lumped Parameter Models of the Cardiovascular System

Cardiovascular models have been developed for disease diagnosis support, the study of cardiovascular physiology, and design optimization of prosthetic devices. However, the wide variety of models can make comparison difficult. This review provides an overview of cardiovascular system models and compares three representative models, based on coupled systems of ordinary differential equations to reproduce hemodynamics implemented within Simulink. The analysis focuses on the model fidelity and capability, in terms of atrial contractility and the activation function of the heart contraction, which have been implemented either only partially or not at all in the original papers. Simulation results revealed that the effect of an atrial kick was neglected in the passive atria model, assuming a linear relationship between the atrium pressure and volume, thereby limiting its ability into a low range of heart rate. A time-varying elastance activation function captured the ventricular pressure–volume (PV) loop but produced an unrealistic atrial PV loop while the inverse was the case for a time-varying pressure model. Adjusting an atrioventricular delay (AVd) is achievable in the contractile atria model, revealing that the optimal AVd is a trade-off between the atrial filling and contraction to maximize the effectiveness of atrial kick to assist complete ventricular filling.