Rabineau Jeremy, Issertine Margot, Hoffmann Fabian, Gerlach Darius, Caiani Enrico G, Haut Benoit, van de Borne Philippe, Tank Jens, Migeotte Pierre-François
LPHYS, Département de Cardiologie, Université Libre de Bruxelles, Brussels, Belgium.
TIPs, École Polytechnique de Bruxelles, Université Libre de Bruxelles, Brussels, Belgium.
Front Physiol. 2022 Oct 7;13:944587. doi: 10.3389/fphys.2022.944587. eCollection 2022.
Microgravity has deleterious effects on the cardiovascular system. We evaluated some parameters of blood flow and vascular stiffness during 60 days of simulated microgravity in head-down tilt (HDT) bed rest. We also tested the hypothesis that daily exposure to 30 min of artificial gravity (1 g) would mitigate these adaptations. 24 healthy subjects (8 women) were evenly distributed in three groups: continuous artificial gravity, intermittent artificial gravity, or control. 4D flow cardiac MRI was acquired in horizontal position before (-9 days), during (5, 21, and 56 days), and after (+4 days) the HDT period. The false discovery rate was set at 0.05. The results are presented as median (first quartile; third quartile). No group or group × time differences were observed so the groups were combined. At the end of the HDT phase, we reported a decrease in the stroke volume allocated to the lower body (-30% [-35%; -22%]) and the upper body (-20% [-30%; +11%]), but in different proportions, reflected by an increased share of blood flow towards the upper body. The aortic pulse wave velocity increased (+16% [+9%; +25%]), and so did other markers of arterial stiffness ( ; ). In males, the time-averaged wall shear stress decreased (-13% [-17%; -5%]) and the relative residence time increased (+14% [+5%; +21%]), while these changes were not observed among females. Most of these parameters tended to or returned to baseline after 4 days of recovery. The effects of the artificial gravity countermeasure were not visible. We recommend increasing the load factor, the time of exposure, or combining it with physical exercise. The changes in blood flow confirmed the different adaptations occurring in the upper and lower body, with a larger share of blood volume dedicated to the upper body during (simulated) microgravity. The aorta appeared stiffer during the HDT phase, however all the changes remained subclinical and probably the sole consequence of reversible functional changes caused by reduced blood flow. Interestingly, some wall shear stress markers were more stable in females than in males. No permanent cardiovascular adaptations following 60 days of HDT bed rest were observed.
微重力对心血管系统有有害影响。我们评估了头低位倾斜（HDT）卧床休息60天期间的一些血流参数和血管僵硬度。我们还测试了每日暴露于30分钟人工重力（1g）可减轻这些适应性变化的假设。24名健康受试者（8名女性）被平均分为三组：持续人工重力组、间歇性人工重力组或对照组。在HDT期之前（-9天）、期间（第5、21和56天）以及之后（+4天）的水平位采集4D流心脏磁共振成像。错误发现率设定为0.05。结果以中位数（第一四分位数；第三四分位数）表示。未观察到组间或组×时间差异，因此将各组合并。在HDT期结束时，我们报告分配到下半身的每搏输出量减少（-30%[-35%；-22%]），上半身减少（-20%[-30%；+11%]），但比例不同，表现为流向身体上部的血流份额增加。主动脉脉搏波速度增加（+16%[+9%；+25%]），其他动脉僵硬度标志物也增加（ ； ）。在男性中，时间平均壁面剪应力降低（-13%[-17%；-5%]），相对停留时间增加（+14%[+5%；+21%]），而在女性中未观察到这些变化。在恢复4天后，这些参数大多趋于或恢复到基线水平。人工重力对策的效果不明显。我们建议增加负荷因子、暴露时间，或将其与体育锻炼相结合。血流变化证实了上半身和下半身发生的不同适应性变化，在（模拟）微重力期间，有更大比例的血容量分配到上半身。在HDT期，主动脉似乎更僵硬，然而所有这些变化仍处于亚临床状态，可能仅是由血流减少引起的可逆性功能变化的唯一后果。有趣的是，一些壁面剪应力标志物在女性中比在男性中更稳定。未观察到60天HDT卧床休息后出现永久性心血管适应性变化。
