Modeling Of Cardiovascular Hemodynamics With A Myocardial Cell Model Incorporated Into A Closed-loop Multi-scale CVS Model

0-1D multi-scale modeling of the cardiovascular system(CVS)has been increasingly recognized to be a versatile and effective method in prediction of both normal and abnormal cardiovascular hemodynamics.Conventional CVS models however employs a simple time-varying elastance model to model the four cardiac chambers of the heart without consideration of the myocardial cell physiology,and thus has limitations in studying the mechanisms of heart diseases.Here we proposed a closedloop multi-scale cardiovascular hemodynamic model with a cardiomyocyte model incorporated.Each of the four cardiac cambers of the heart was approximated to have a thin-walled hemisphere geometry,which was modeled to perform the cardiac contraction of cardiac muscle cells and sarcomere by combining a cardiomyocyte electrophysiological model and a cross-bridge dynamics model.Ventricles and atrial pressures were calculated based on Laplace's law to achieve the transformation from myocardial cell strains to ventricle contraction.Macroscopic hemodynamic functions in terms of the pressure-volume waveform and the valve flow waveform of ventricles and atrium were simulated and compared with the observations of normal human body;microscopic electrophysiological characteristics of the cardiac cells were capable of capturing the peak shape of the cardiomyocyte action potential,the instantaneous peak of calcium ion,and the microscopic ion currents in the cells.Although further validation of the proposed model is necessary to confirm its capability in predicting microscopic electrophysiological and macroscopic hemodynamic characteristics,the current model demonstrates a possibility of the 0-1D CVS model's application in unveiling the mechanisms associated with cardiomyocytes-based cardiovascular diseases.With the CVS hemodynamic model we further made an analysis on the effects of anesthesia-induced thermoregulatory system damage and the low temperature environment of the operating room on the perioperative thermoregulation of individualized patients.We combined a simple anesthesia model and an authoritative individualized thermoregulatory model to assess the effects of individualized characteristics such as age,obesity,and cardiovascular disease on thermoregulation.We found that in low temperature environment,compared with young people,the elderly showed a trend with lower core temperatures and higher body surface temperatures.Moreover,our results demonstrated that a reduction in the threshold setting of vasoconstrictions by about 0.5-3° C led to a significant decrease in core temperature.This indicates that the individualized characteristics of the body have an important impact on human body temperature in a low temperature environment,which implies that a combination of individual signs and general anesthesia may complicate the body's thermoregulation while being of significant challenges for clinicians.