Microgravity-induced alterations in left atrial hemodynamics and thrombogenic risk: Insights from healthy and atrial fibrillation models

Document Type

Article

Publication Date

6-1-2026

Abstract

Background: Microgravity exposure alters cardiovascular loading, yet its impact on left atrial flow dynamics and thrombotic risk remains poorly understood. This study investigates how spaceflight-relevant microgravity-induced changes in cardiac outflow affect left atrial hemodynamics in healthy individuals and patients with atrial fibrillation. Methods: Patient-specific left atrial models were generated for three healthy individuals and three AF patients. Computational fluid dynamics (CFD) simulations were performed using each patient's baseline mitral outflow waveform and two modified waveforms representing short- and long-duration post-flight cardiac loading changes derived from echocardiographic observations. Hemodynamic metrics included left atrial velocity, time averaged wall shear stress, oscillatory shear index, relative residence time, and stasis volume, which were used to assess thrombogenic flow conditions. Results: Post-flight, microgravity-associated modifications to mitral outflow conditions produced distinct hemodynamic responses across cohorts. In healthy individuals, short-duration post-flight loading reduced time-averaged wall shear stress from 1.51 to 1.00 Pa and increased velocity-defined stasis from 19.6 % to 64.2 %, indicating substantially reduced atrial washout. Under long-duration post-flight conditions, these metrics recovered toward or above baseline values (time-averaged wall shear stress 1.68 Pa; stasis 18.5 %), consistent with hemodynamic adaptation. In contrast, patients with atrial fibrillation exhibited high baseline stasis and showed minimal changes in time-averaged wall shear stress, oscillatory shear, or relative residence time across all loading conditions. Across all cohorts, the left atrial appendage consistently demonstrated the lowest shear and highest residence time. Conclusion: These findings indicate that spaceflight-related microgravity exposure may transiently increase atrial flow stasis and thrombotic risk in individuals with normal atrial function, while individuals with atrial fibrillation remain in a persistently high-risk hemodynamic state that is relatively insensitive to microgravity-induced loading changes. This study provides the first patient-specific, chamber-level computational assessment of how spaceflight-documented cardiac adaptations influence left atrial hemodynamics and highlights the importance of accounting for duration-dependent hemodynamic adaptation when assessing thrombotic risk associated with human spaceflight.

Publication Title

Acta Astronautica

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