Objective: To study the effects of depressed myocardial contractility induced by microgravity on cardiovascular response to orthostatic stress, and to investigate the role played by the changes of myocardial contractility in the mechanism of cardiovascular deconditioning and orthostatic intolerance induced by space weightlessness.
Method: On the basis of our previous model used to simulate the cardiovascular response to lower body negative pressure (LBNP), the factor of changes of myocardial contractility was incorporated into the model by multiplying a coefficient to the maximum elastance of the heart working sub-model. By decreasing the coefficient progressively, then 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 total blood volume were simulated.
Result: Simulation results indicated that depressed myocardial contractility induces more augment of HR, and more decrease of BP and CO during LBNP.
Conclusion: The depression of myocardial contractility degenerated cardiovascular response to orthostatic stress.