In recent years, a variety of models that couple 3D whole heart electromechanics to a 0D circulation model have been published. In general, these models are able to reproduce major features and phases of human circulation. However, they are lacking physiological detail regarding pressure and flow across the valves, since they are typically modeled as a diode with a characteristic resistance.
To alleviate this shortcoming of the circulation models, we implement a model of heart valve dynamics based on Bernoulli's principle to account for the transvalvular pressure drop and combine it with a model to control opening and closing of the valves based on pressure differences. We evaluate the new model based on a simulation with healthy valves and explore the possibility of simulating heart valve diseases by considering a case of severe aortic stenosis.
We show that the model more faithfully reproduces pressure, volume, and flow in all four chambers and in particular across the valves. Most of the changes are related to the consideration of blood inertia. However, we are able to show that only by opening and closing the valves more slowly, it is possible to reproduce features connected to backflow such as the dicrotic notch. When reducing the maximum area ratio of the aortic valve to 10%, a pressure gradient of 77.2 mmHg across the aortic valve during systole and a 20% reduction in stroke volume was observed in accordance with the AHA guidelines of severe aortic stenosis.
To conclude, we were able to improve our existing 0D circulation model in terms of physiological accuracy by replacing the diode-like valves with an easy to implement model of heart valve dynamics that is capable of simulating both healthy and pathological scenarios.