Investigation of raphe function in the bicuspid aortic valve and its influence on clinical criteria—A patient‐specific finite element study

• Published in: International journal for numerical methods in biomedical engineering 2018-10, Vol.34 (10), p.e3117-n/a
• Main Authors: Dallard, Jérémy, Labrosse, Michel R., Sohmer, Benjamin, Beller, Carsten J., Boodhwani, Munir
• Format: Article
• Language: English
• Subjects: Algorithms; Aorta - anatomy & histology; Aorta - physiopathology; Aortic valve; Aortic Valve - abnormalities; Aortic Valve - physiopathology; bicuspid aortic valve; Bicuspid Aortic Valve Disease; Biomechanical Phenomena; Computer simulation; Cusps; Diastole; Diastole - physiology; Echocardiography; Esophagus; Female; Finite Element Analysis; Finite element method; finite element study; Geometry; Heart Valve Diseases - physiopathology; Humans; Male; Material properties; Mathematical analysis; Mathematical models; Middle Aged; Models, Cardiovascular; organ function; Patients; raphe; Severity of Illness Index; soft tissues modeling; Stiffness; Stress analysis; Stress concentration; Stress distribution; Surgery; Systole; Systole - physiology; Tricuspid Valve - physiology
• ISSN: 2040-7939; 2040-7947
• DOI: 10.1002/cnm.3117

The aortic valve is normally composed of 3 cusps. In one common lesion, 2 cusps are fused together. The conjoined area of the fused cusps is termed raphe. Occurring in 1% to 2% of the population, the bicuspid aortic valve (BAV) is the most common congenital cardiac malformation. The majority of BAV patients eventually require surgery. There is a lack in the literature regarding modeling of the raphe (geometry and material properties), its role and its influence on BAV function. The present study aims to propose improvements on these aspects. Three patient‐specific finite element models of BAVs were created based on 3D trans‐esophageal echocardiography measurements, and assuming age‐dependent material properties. The raphe was initially given the same material properties as its underlying cusps. Two levels of validation were performed; one based on the anatomical validation of the pressurized geometry in diastole (involving 7 anatomical measures), as simulated starting from the unpressurized geometry, and the other based on a functional assessment using clinical measurements in both systole and diastole (involving 16 functional measures). The pathology was successfully reproduced in the FE models of all 3 patients. To further investigate the role of the raphe, 2 additional scenarios were considered; (1) the raphe was considered as almost rigid, (2) the raphe was totally removed. The results confirmed the interpretation of the raphe as added stiffness in the fused cusp's rotation with respect to the aortic wall, as well as added support for stress distribution from the fused cusps to the aortic wall. Occurring in 1‐2% of the population, the bicuspid aortic valve (BAV) is the most common congenital cardiac malformation. There is a need to better understand BAV biomechanics, with direct applications in surgery. The first patient‐specific BAV models with raphe were created and analyzed. The findings support the use of material properties for the prolapsing raphe that are identical to the cusps'. The results also confirm the interpretation of the raphe as added stiffness in the fused cusp's rotation with respect to the aortic wall, as well as added support for stress distribution from the fused cusps to the aortic wall.