Atherogenic potential of microgravity hemodynamics in the carotid bifurcation: a numerical investigation

Abstract

Long-duration spaceflight poses multiple hazards to human health, including physiological changes associated with microgravity. The hemodynamic adaptations occurring upon entry into weightlessness have been associated with retrograde stagnant flow conditions and thromboembolic events in the venous vasculature but the impact of microgravity on cerebral arterial hemodynamics and function remains poorly understood. The objective of this study was to quantify the effects of microgravity on hemodynamics and wall shear stress (WSS) characteristics in 16 carotid bifurcation geometries reconstructed from ultrasonography images using computational fluid dynamics modeling. Microgravity resulted in a significant 21% increase in flow stasis index, a 22–23% decrease in WSS magnitude and a 16–26% increase in relative residence time in all bifurcation branches, while preserving WSS unidirectionality. In two anatomies, however, microgravity not only promoted flow stasis but also subjected the convex region of the external carotid arterial wall to a moderate increase in WSS bidirectionality, which contrasted with the population average trend. This study suggests that long-term exposure to microgravity has the potential to subject the vasculature to atheroprone hemodynamics and this effect is modulated by subject-specific anatomical features. The exploration of the biological impact of those microgravity-induced WSS aberrations is needed to better define the risk posed by long spaceflights on cardiovascular health.

Numerical analysis of blood flow in the abdominal aorta under simulated weightlessness and earth conditions

“…Microgravity does not radically change OSI distribution at rest or during moderate exercise 76 , 77 . A healthy abdominal aorta is typically indicated by an OSI value of zero, which occurs in the primary oscillating blood flow.…”

“…In our results, this decrease is approximately 22% during exercise and 28% at rest for the mean TAWSS. Sucosky et al 77 reported an average change in TAWSS of 22% for the common carotid artery. An important finding is that performing exercises in a state of weightlessness results in much higher values of wall shear stress compared to those during rest in the presence of Earth’s gravity.…”

Role of Preoperative Ultrasound Shear-Wave Elastography and Radiofrequency-Based Arterial Wall Tracking in Assessing the Vulnerability of Carotid Plaques: Preliminary Results

“…The application of ultrasound techniques for the functional assessment of mechanical properties of vessel walls in the understanding of major atherosclerotic diseases has progressively gained increasing appeal among medical researchers [19] thanks to its wide in vivo applicability [20].…”

Technology using simulated microgravity

“…This allows for a better understanding of various phenomena in microgravity environments while saving costs and time for experiments and research. However, in humans, gravity is an important component of biological functions such as those of the heart, nerves, and bones, and the effects of microgravity on the development and function of these tissues are largely unexplored [ [7] , [8] , [9] ]. The relationship between these tissues lies in their interconnectedness within the human body.…”