Effects of depressed myocardial contractility induced by microgravity on cardiovascular response to orthostatic stress: a computer simulation

The aim of present study is to investigate the role played by the depression of myocardial contractility in the mechanism of cardiovascular deconditioning and orthostatic intolerance (OI) induced by space weightless-ness. Based on our previous model, which was used to simulate cardiovascular response to lower body negative pressure (LBNP), we incorporated the factor of changes of myocardial contractility into the model by multiplying a coefficient to the time-varying elastance that represents the changes of cardiac contractility. By decreasing the coefficient progressively, we simulated the changes of heart rate (HR), blood pressure (BP), and cardiac output (CO) during LBNP after 0-30% of myocardial contractility depression combined with 12% decrease of the total blood volume. Simulation results indicate that depressed myocardial contractility induces more augment of HR, and more decrement of BP and CO during LBNP and suggest that the depression of myocardial contractility degenerate cardiovascular response to orthostatic stress.