ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

since they are much stiffer than the elastin and have higher stress than their
surroundings. The plots of t=30ms represent the beginning of the opening phase when
the pressure in the ventricle is only slightly larger than the pressure in the aorta and the
large flow velocity from the ventricle opens the valve. Later in the opening phase
(t=70ms) the larger pressure difference on the belly region keeps on the opening. This
type of opening, that starts from the belly region and carry on to the coapting region, is
very dependent on the locations and directions of the fibres and on the mechanical
properties of the elastin and the collagen. At the same time, a contact between the
leaflets is found near the commissures. These regions are in contact throughout the
systolic phase. At the end of the systolic phase (t=160ms) the direction of the flow starts
to reverse and a low velocity regions are found in the sinuses. During the systolic phase
the pressure difference is almost zero. At the closing phase (t=220ms) the large pressure
difference on the leaflets closes the valve and the flow direction is from the aorta to the
left ventricle. During the closing phase, the contact region starts from the commissures
to the centre of the leaflets. The valve is fully closed by (t=270ms) when the coaptation
between the leaflets can be clearly seen in the 2D section. The large pressure difference
between the two sides of the valve (approximately 100mmHg) leads to the creation of
larger stress in the belly region and near the commissures relative the stress in the
coapting region. A possible explanation is the negligible pressure difference in this
region.
5. CONCLUSIONS
A 3D FSI model of natural aortic valve with compliant root, physiological blood
pressure and realistic material properties has been developed. The model includes the
opening, systolic, closing and diastolic phases of the cardiac cycle. This model allows,
for the first time, to model accurately the aortic valve kinematics and dynamics in
realistic conditions. The results show that a correct contact modelling is needed even in
the systolic phase. The tissue model, that accounts for the hyperelasticity and the local
directions of the collagen, has a major effect on the opening and closing kinematics.