Aortic Biological Prosthetic Valve for Open-Surgery and Percutaneous Implant: Procedure Simulation and Performance Assessment - Cardiovascular and Cardiac Therapeutic Devices - page 145

1. after transecting the ascending aorta for exposure, the diseased valve is excised;
2. the aortic annulus is sized with a dedicated aortic valve sizer;
3. stay sutures are placed and, subsequently, the valve is lowered: the prosthesis
takes its position supra-annularly.
On the basis of the operative steps of the real procedure, we adopted a simu-
lation strategy which can be described in four principal steps:
1. a parametric CAD model of the supra-annular prosthesis is properly created;
2. the CAD model of the aortic root is obtained from DICOM images of contrast-
enhanced computed tomography-angiography (CT-A) through dedicated image
processing;
3. the AVR operation is mimicked by positioning the stentless tissue valve inside
the aortic root through a placement simulation;
4. finally, a second simulation considering both aortic root and valve is performed
to evaluate valve competence during diastole.
In particular, we simulate the implant of three different sizes of the Freedom
Solo (Sorin Biomedica Cardio, Saluggia, Italy) stentless valve, starting from a
single patient-specific aortic root model. In the following, we discuss each of listed
operative steps, while more details are reported in [ 6 ].
4.1.2 Stentless Prosthesis Model
As stated by Xiong et al. (2010), the prosthetic leaflet geometry plays a key-role for
efficacy and durability in AVR procedures and, for this reason, it is important to
accurately reproduce it in order to predict the realistic valve behavior. In our case,
given the lack of specific technical data from the manufacturer, we generate the
model of the stentless valve assuming that the three leaflets to be implanted in the
patient's aortic root have the same geometrical features as a healthy native AV [ 9 ].
Even though modeling the stentless prosthesis simply respecting the geometrical
properties of healthy valves does not allow very accurate reconstructions of the
prosthetic device, we believe that this simplifying assumption does not affect the
methodological approach we would like to discuss herein. Indeed, at the same time,
we think that future developments to achieve more precise geometrical models of
the prosthesis have to be addressed to obtain simulation results closer to reality.
Herein, for the sake of simplicity, the Labrosse's geometrical guidelines are
adopted to define the model [ 68 ] hence our model of the prosthetic leaflets is
completely described by the following five parameters [ 5 ] (see Fig. 7 ):
• diameter of the annulus, D a ;
• diameter of the top of the commissure, D c ;
• valve height, H;
• leaflet free margin length, L fm ;
• leaflet height, L h .