Elasticity/distensibility of the ascending aorta: basal conditions and simulated conditions from space flights

Introduction: The hysto-mor- fological composition of the ascending aorta wall gives to the vessel its characteristic elastic- ity/distensibility, which is deteriorated due to both physiological (age) and pathological events (hypertension, diabetes, dyslipidemia). This con- tributes to reduce the wall elasticity and to oc- currence of cardiovascular events. Matherials and Methods: Thirty young healthy subjects (20 males, 10 females, age <30 yr), were subjected to different postural conditions with and without Lower Body Negative Pressure (LBNP) with conventional procedures, to simulate the microgravity conditions in space flight. During this procedure the cardiovascular parameters and the aorta elasticity were assessed with eco- cardiography. Results: The observation of results and sta- tistical comparison showed that despite differ- ent hemodynamic conditions and with signifi- cant variation of blood pressure related to pos- ture, elasticity/distensibility did not change sig- nificantly. Discussion: The elasticity/distensibility of ar- terial vessels is the result of two interdependent variables such as blood pressure and systolic and diastolic diameters. While blood pressure and heart rate vary physiologically in relation to posture, the compensation of the vessel diame- ters modifications maintains the aortic compli- ance invariate. Therefore, in young healthy peo- ple, despite the significant postural and the sud- den pressure changes (equivalent to parietal stress) aortic compliance does not alter. This be- havior might be related to the low rate of cardio- vascular events that are present in healthy peo- ple aged under 30 yrs.