The concept of aortic replacement based on computational fluid dynamic analysis: patient-directed aortic replacement.

OBJECTIVES: Aortic replacement is based on the aortic diameter in the absence of dissection or connective tissue diseases. Frequently, a number of different aortic-to-prosthetic anastomotic positions are possible depending on patient factors and surgeon preferences. High stress on residual aortic tissue may result in aneurysm formation or aneurysmal dilatation. Utilizing a computational fluid dynamic evaluation, we aimed to define possible optimal operative interventions with regard to the extent of aortic replacement.
METHODS: For proof of principle, a computational fluid dynamic (CFD) analysis, using Fluent 6.2 (Ansys UK Ltd, Sheffield, UK), was performed on a simplified ascending arch and descending aortic geometry. Wall shear stress in three dimensions was assessed for the standard operations: ascending aortic replacement, arch replacement and proximal descending aortic replacement.
RESULTS: Hermiarch replacement is superior to isolated ascending aortic replacement with regard to residual stress analysis on tissues (up to a 10-fold reduction). Aortic arch replacement with island implantation of the supra-aortic vessels may potentially result in high stress on the residual aorta (10-fold increase). Aortic arch replacement with individual supra-aortic vessel implantation may result in areas of high stress (10-fold increase) on native vessels if an inadequate length of supra-aortic tissue is not resected, regardless of it being aneurysmal.
CONCLUSIONS: Computational fluid dynamic evaluation, which will have to be patient-specific, 3D anatomical and physiological, potentially has enormous implications for operative strategy in aortic replacement surgery. CFD analysis may direct the replacement of normal-diameter aortas in the future.