Opening Pattern of Bicuspid Aortic Valve Influences Hemodynamics of the Aorta and Wall Shear Stress: A Left Ventricle-Aortic Valve-Aorta Computational Model Study
Koichi Sughimoto1, Takashi Fujiwara2, Alex J Barker3, ShinzoTorii1, Tadashi Kitamura1, Mamika Motokawa1, Yurie Miyata1, Kagami Miyaji1, Hao Liu2.
1.Kitasato University School of Medicine, Sagamihara, JAPAN; 2.Chiba University, Chiba, Japan; 3.Northwestern University, Chicago, IL, USA.
Bicuspid aortic valve is known to cause the dilatation of the ascending aorta, resulting in rupture or dissection of the aorta. The relationship between the morphological impact of the bicuspid aortic valve and the hemodynamics is not fully understood. A multiscale hemodynamic model was created incorporating an MRI morphological data and bicuspid aortic valve.
A multiscale computational biomechanical model was devised by using MRI three-dimensional structure including the left ventricle to the aortic arch in one cardiac cycle. Three types of the aortic valve were designed as normal tricuspid and bicuspid opening parallel and perpendicular to the mitral valve alignment. A patient-specific model of bicuspid aortic valve (RN fusion) was also created. Pathlines in the aorta, wall shear stress (WSS) and oscillatory shear index (OSI) were compared among three models. The pathlines of the patient-specific model (RN fusion-bicuspid) was compared to the MRI.
While normal tricuspid valve model showed smooth pathlines and low WSS, the both bicuspid aortic valve showed a locally intensified, helical systolic flow jet and elevated WSS on the anterior aspect of the ascending aorta. OSI was elevated at the lateral wall of the aortic root in the parallel model, anterior wall in the perpendicular model. In the RN fused bicuspid model, the pathlines showed crock-wise flow jet with intensified jet toward the superior, anterior aspect of the ascending aorta along with the largest WSS in the same location, while OSI was lowest in the corresponding locations.
The orientation of valve opening influenced the flow pattern in the aorta as well as WSS and OSI. Bicuspid aortic valve was associated with the alteration of local flow and wall shear stress, these features may be one of the causes of the mechanical change of the aortic wall. Moreover, the flow pattern in the patient model was more complicated than the simplified BAV models. Further investigations are necessary with regard to the computation of patient-specific models of other bicuspid aortic valve phenotypes.