Emboli transport in a full patient-specific aortic tree: Assessment of abdominal organ injury risk during cardiopulmonary bypass.

BACKGROUND AND OBJECTIVE: Cardiopulmonary bypass (CPB), though indispensable in cardiac surgery, carries significant risks of systemic embolization and organ injury. While cerebral and cardiac complications have been thoroughly investigated, the impact of emboli on abdominal organs remains largely unexplored. This study aims to identify hemodynamic and embolus-related factors governing embolic transport to key abdominal arteries during CPB, using computational modeling in a patient-specific aortic anatomy.

METHODS: A validated OpenFOAM-based computational fluid dynamics (CFD) framework was integrated with Lagrangian particle tracking (LPT) and applied under steady, pump-driven flow conditions representative of CPB to simulate embolic trajectories within a patient-specific aorta. Parametric analyses were conducted to evaluate the individual effects of blood flow rate (3-5 LPM), hemodiluted blood viscosity (1.5-3.5 cP), and embolus size (0.5-2.5 mm) on embolic distribution across major abdominal aortic branches including the renal, hepatic, splenic, mesenteric, and iliac arteries.

RESULTS: Lower blood viscosity (1.5 cP) and higher CPB flow rate (5 LPM) significantly influenced embolic transport, both independently and in combination. Under combined conditions, emboli transport to the renal and hepatic arteries increased from 17% to 27% and from 7.1% to 10.7%, respectively. Reduced viscosity alone produced the greatest rise, with increases of 18% and 35% in the renal and hepatic arteries. Increasing CPB flow rate from 3 to 5 LPM also elevated emboli exit across all branches, with renal transport rising by 29%. Also, larger emboli (2.5 mm) exhibited higher escape rates of 14% and 26% into the renal and hepatic arteries, respectively, compared to smaller emboli. These tendencies are consistent with trends reported in clinical studies of post-CPB complications.

CONCLUSIONS: This study presents the first CFD-based analysis of embolic transport to the abdominal organs during CPB, revealing critical pathways previously overlooked in both clinical and computational research. The results demonstrate that lower blood viscosity, higher CPB flow rates, and larger emboli significantly increase embolic dispersion into abdominal arteries. To mitigate these potential risks, this study highlights the need for optimized CPB perfusion strategies to minimize embolic burden and improve intraoperative protection of abdominal organs during cardiac surgery.