Aortic flow and morphology adaptation to deconditioning after 21-days of head-down bed-rest assessed by phase contrast MRI

Our aim was to assess the effects of 21-days head-down (-6 degrees) bed-rest (BR) and effectiveness of sledge jump countermeasure (CM), on aortic flow and morphology by Phase Contrast (PC) MRI. Male subjects were enrolled at :envihub (DLR, Germany) in control (CTRL, N=12) or countermeasure (CM, N=12) groups. PC-MRI images were obtained before and after 21-days of BR, and analyzed with custom software. Semi-automated region growing and thresholding were applied to segment the aortic lumen, and to compute parameters from velocity images: area lumen (AL), flow velocity, stroke volume (SV), flow rate (Qpeak), time-to-peak flow, systolic duration and heart beat duration (RR). After 21 days, in CTRL significant decreases in SV (14%), Qpeak (5%) and AL (4%) were observed compared to baseline values. Conversely, for CM no changes were observed in these parameters, but only in RR (-8%). Cardiac adaptation to deconditioning due to immobilization resulted in a reduction of SV and Qpeak that might have induced a remodeling process in the ascending aorta, by shrinking of its lumen. The applied CM seemed to counteract at least partially these effects.