A computational fluid dynamics model of a bicuspid aortic valve has been developed using idealised three-dimensional geometry. The aim was to compare how the orifice area and leaflet orientation affect the hemodynamics of a pure bicuspid valve. By applying physiologic material properties and boundary conditions, blood flow shear stresses were predicted during peak systole. A reduced orifice area altered blood velocity, the pressure drop across the valve and the wall shear stress through the valve. Bicuspid models predicted impaired blood flow similar to a stenotic valve, but the flow patterns were specific to leaflet orientation. Flow patterns developed in bicuspid aortic valves, such as helical flow, were sensitive to cusp orientation. In conclusion, the reduced opening area of a bicuspid aortic valve amplifies any impaired hemodynamics, but cusp orientation determines subsequent flow patterns which may determine the specific regions downstream from the valve most at risk of clinical complications.
WardC. Clinical significance of the bicuspid aortic valve. Heart2000; 83: 81–85.
4.
FedakPVermaSDavidT. Clinical and pathophysiological implications of a bicuspid aortic valve. Circulation2002; 106: 900–904.
5.
SieversHHSchmidtkeC. A classification system for the bicuspid aortic valve from 304 surgical specimens.J Thorac Cardiovasc Surg2007; 133: 1226–1233.
6.
RobicsekFThubrikarMJCookJW. The congenitally bicuspid aortic valve: how does it function? Why does it fail?Ann Thorac Surg2004; 77: 177–185.
7.
KuanMYSEspinoDM. Systolic fluid-structure interaction model of the congenitally bicuspid aortic valve: assessment of modelling requirements. Comput Methods Biomech Biomed Eng2015; 18: 1305–1320.
8.
JermihovPNJiaLSacksMS. Effect of geometry on the leaflet stresses in simulated models of congenital bicuspid aortic valves. Cardiovasc Eng Technol2011; 2: 48–56.
9.
DemerLLTintutY. Vascular calcification: pathobiology of a multifaceted disease. Circulation2008; 117: 2938–2948.
10.
VergaraCViscardiFAntigaL. Influence of bicuspid valve geometry on ascending aortic fluid dynamics: a parametric study. Artif Organs2012; 36: 368–378.
11.
ViscardiFVergaraCAntigaL. Comparative finite element model analysis of ascending aortic flow in bicuspid and tricuspid aortic valve. Artif Organs2010; 34, 1114–1120.
12.
MaromGKimHSRosenfeldM. Fully coupled fluid–structure interaction model of congenital bicuspid aortic valves: effect of asymmetry on hemodynamics. Med Biol Eng Comput2013; 51: 839–848.
13.
SchaeferBMLewinMBStoutKK. The bicuspid aortic valve: an integrated phenotypic classification of leaflet morphology and aortic root shape. Heart2008; 94: 1634–1638.
BissellMMHessATBiasiolliL. Aortic dilation in bicuspid aortic valve disease flow pattern is a major contributor and differs with valve fusion type. Circ Cardiovasc Imaging2013; 6: 499–507.
17.
De HartJPetersGWSchreursPJ. A three-dimensional computational analysis of fluid-structure interaction in the aortic valve. J Biomech2003; 36: 103–112.
18.
HagerAKaemmererHBernhardtU. Diameters of the thoracic aorta throughout life as measured with helical computed tomography. J Thorac Cardiovasc Surg2002; 123: 1060–1066.
19.
LevickJR. An introduction to cardiovascular physiology. Butterworth-Heinemann, Oxford; 1995.
20.
ChandraSRajamannanNMSucoskyP. Computational assessment of bicuspid aortic valve wall-shear stress: implications for calcific aortic valve disease. Biomech Model Mechanobiol2012; 11: 1085-1096.
21.
CallejaAThavendiranathanPIonasecRI. Automated quantitative 3-dimensional modeling of the aortic valve and root by dimensional transesophageal echocardiography in normals, aortic regurgitation and aortic stenosis: comparison to computed tomography in normals and clinical implications. Circ Cardiovasc Imaging2013; 6: 99-108.
22.
SwansonWMClarkRE. Dimensions and geometric relationships of the human aortic value as a function of pressure. Circ Res1974; 35: 871-882.
23.
Haj-AliRMaromGBen ZekryS. A general three-dimensional parametric geometry of the native aortic valve and root for biomechanical modeling. J Biomech2012; 45: 2392-2397.
24.
ChandranKBVigmostadSC. Patient-specific bicuspid valve dynamics: overview of methods and challenges. J Biomech2013; 46: 208–216.
25.
WeinbergEJKaazempur-MofradMR. A multiscale computational comparison of the bicuspid and tricuspid aortic valves in relation to calcific aortic stenosis. J Biomech2008; 41: 3482-3487.
26.
GorlinRGorlinS. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves and central occluding shunts. Am Heart J1951; 41: 1-29.
27.
ChandranKBRittgersSEYoganathanAP. Biofluid mechanics: The human circulation. CRC Press, Boca Raton; 2007.
28.
CaroCGPedleyTJSchroterRC. The mechanics of the circulation. Cambridge University Press, Cambridge; 2012.
29.
CartyGChatpunSEspinoDM. Modeling blood flow through intracranial aneurysms: a comparison of Newtonian and non-Newtonian viscosity. J Med Biol Eng2016; Epub, DOI:10.1007/s40846-016-0142-z.
SteinPDSabbahHN. Turbulent blood flow in the ascending aorta of humans with normal and diseased aortic valves. Circ Res1976; 39: 58-65.
32.
PatelDJVaishnevRNAtabekHB. Local mechanical properties of the vascular intima and adjacent flow field. In: HwangNHCGrossDRPatelDJ (eds) Quantitative Cardiovascular Studies, University Park Press, Baltimore; 1979.
33.
OhJKTaliercioCPHolmesDRJr. Prediction of the severity of aortic stenosis by Doppler aortic valve area determination: prospective Doppler-catheterization correlation in 100 patients. J Am Coll Cardiol1988; 11:1227-1234.
34.
SabetHYEdwardsWDTazelaarHD. Congenitally bicuspid aortic valves: a surgical pathology study of 542 cases (1991 through 1996) and a literature review of 2,715 additional cases. Mayo Clin Proc1999; 74:14–26.
35.
RichardsKEDeserrannoDDonalE. Influence of structural geometry on the severity of bicuspid aortic stenosis. Am J Physiol Heart Circ Physiol2004; 287: H1410-H1416.
36.
WestonMWLaBordeDVYoganathanAP. Estimation of the shear stress on the surface of an aortic valve leaflet. Ann Biomed Eng1999; 27: 572-579.
37.
YapCHSaikrishnanNYoganathanAP. Experimental measurement of dynamic fluid shear stress on the ventricular surface of the aortic valve leaflet. Biomech Model Mechanobiol2012; 11: 231-244.
38.
ManningW J. Asymptomatic aortic stenosis in the elderly: a clinical review. JAMA2013; 310: 1490-1497.
39.
VahanianAAlfieriOandreottiF. Guidelines on the management of valvular heart disease. Eur Heart J2012; 33: 2451-2496.
40.
Della CorteABanconeCContiCA. Restricted cusp motion in right-left type of bicuspid aortic valves: a new risk marker for aortopathy. J Thorac Cardiovasc Surg2012; 144: 360-369.
41.
ToriiRXuXYEl-HamamsyI. Computational biomechanics of the aortic root. Aswan Heart Cent Sci & Prac Series2011; 16.
42.
MalekAMAlperSLIzumoS. Hemodynamic shear stress and its role in atherosclerosis. J Am Med Assoc1999; 282: 2035-2042.
43.
PastaSRinaudoALucaA. Difference in hemodynamic and wall stress of ascending thoracic aortic aneurysms with bicuspid and tricuspid aortic valve. J Biomech2013; 46: 1729–1738.
44.
RussoCFCannataALanfranconiM. Is aortic wall degeneration related to bicuspid aortic valve anatomy in patients with valvular disease?J Thorac Cardiovasc Surg2008; 136: 937-942.
45.
BalachandranKSucoskyPYoganathanAP. Hemodynamics and mechanobiology of aortic valve inflammation and calcification. Int J Inflam2011: 263870.
46.
OlszowskaM. Pathogenesis and pathophysiology of aortic valve stenosis in adults. Pol Arch Med Wewn2011; 121: 409-413.
47.
EspinoDMShepherdDETHukinsDWL. Development of a transient large strain contact method for biological heart valve simulations. Comput Methods Biomech Biomed Eng2013; 16: 413-424.
48.
Al-AtabiMEspinoDMHukinsDWL. Computer and experimental modelling of blood flow through the mitral valve of the heart. J Biomech Sci Eng2010; 5: 78-84.
49.
EspinoDMShepherdDETHukinsDWL. Evaluation of a transient, simultaneous, Arbitrary Lagrange Euler based multi-physics method for simulating the mitral heart valve. Comput Methods Biomech Biomed Eng2014; 17: 450-458.
50.
EspinoDMShepherdDETHukins. Transient large strain contact modelling: a comparison of contact techniques for simultaneous fluid-structure interaction. Eur J Mech B/Fluids2015; 51: 54-60.
51.
BahrasemanHGHassaniKKhosraviA. Combining numerical and clinical methods to assess aortic valve hemodynamics during exercise. Perfusion2014; 29: 340-350.
