High-G coronary hemodynamics: Effects of bifurcation anatomy and acceleration direction

Repeated high-G exposure is a health risk factor for high-performance fighter pilots, increasing the likelihood of adverse cardiovascular events. Current aviation cardiovascular research primarily focuses on overall cardiac compensation, yet coronary hemodynamics remain incompletely understood. This study aims to investigate the hemodynamic responses of left anterior descending (LAD) and left circumflex (LCx) arteries with varying bifurcation angles under high-G acceleration. Computational fluid dynamics simulations are carried out for LAD–LCx branch models under high-G conditions with varying magnitudes and directions. High-G effects have been incorporated through an acceleration body-force term and corresponding hydrostatic pressure corrections, with inlet velocity and outlet pressure adjusted for various acceleration levels. The results demonstrate a nonlinear correlation between bifurcation angles and atherosclerosis risk. Under Earth's gravity, the 85° bifurcation exhibits the highest risk in the LAD branch, associated with relatively weaker and less coherent helical flow, pronounced high-velocity core deflection, and increased low time-averaged wall-shear stress (TAWSS) exposure. Under +4 Gz condition, the risk associated with obtuse bifurcations increases markedly, accompanied by weakened helical flow and expanded low-TAWSS regions. A 30° reclined posture partially restores helical flow and reduces low-TAWSS exposure to approximately the level observed under +1 Gz. The Gx acceleration strengthens helical flow and increases high-TAWSS exposure near the bifurcation carina. This study reveals that high +Gz amplifies the adverse hemodynamic effects through changes in helical-flow intensity and wall-shear patterns, while seat recline under +Gz reduces the risk of atherosclerosis. Acceleration direction also plays a distinct role, with Gx acceleration increasing the risk of endothelial injury.