Evaluation of Aortic Stiffness as a Prognostic Indicator of Aortic Dilatation in Patients With Bicuspid Aortic Valve by Multimodal Imaging
Evaluation of Aortic Stiffness as a Prognostic Indicator of Aortic Dilatation in Patients With Bicuspid Aortic Valve by Multimodal Imaging
The objective is the development and validation of morphological markers informative of
 aortic dilatation in order to improve the precision of the risk of aneurysm of the thoracic
 aorta and of acute aortic syndrome for patients with bicuspid aortic valve (BAV).

 The primary objective of this study is to demonstrate a correlation between the aortic local
 pulse wave velocity (PWV) measured with MRI and the progression of the thoracic aorta
 diameters measured by MRI after a follow-up of 2 years.
Background Bicuspid Aortic Valve (BAV) is the most common congenital heart defect with
 prevalence around 1 to 2% of the general population . It is defined by the presence of two
 functional cusps with less than three parallel zones of apposition between the cusps. This
 different valve's morphology is associated with a spectrum of valvular (aortic stenosis and
 insufficiency) and aortic complications (aneurysm and dissection). Indeed, the valvular
 abnormality is associated with changes in the aortic arch with an increase in the incidence
 of ascending aortic aneurysm unrelated to valvular functional impairment. The mechanisms
 responsible for aortic involvement are still incompletely understood but combine, in varying
 proportions, a constitutional fragility (linked to a common embryological origin of the
 aortic valve and the aortic arch) and to the haemodynamic modifications, generated by the
 specific morphology of BAV .

 Current risk prediction of aneurysm development is currently performed only with the
 ascending aortic diameter, associated with history of aortic coarctation and familial history
 of dissection. Moreover, aortic dilatation may occur after aortic valve replacement alone,
 necessitating a second intervention, with a higher surgical risk. Improvement of the
 aortopathy evaluation is therefore a major stake in the evaluation of the BAV patient.

 Studies of the biomechanical properties of the BAV aortic wall converge towards an increase
 in arterial stiffness as well as in other elastopathies such as Marfan's disease. Thus,
 measurements of aortic distensibility in trans-thoracic echocardiography (TTE) or MRI, or the
 measurement of the Pulse Wave Velocity (PWV) are significantly different case of BAV compared
 to the general population. However, no prospective study has demonstrated the prognostic role
 of these morphological biomarkers in the prediction of aortic dilation.

 From a biomechanical point of view, the vessel's rupture appears when the mechanical stress
 applied to the wall exceeds the material resistance properties. The aortic resistance
 evaluation requires the use of different imaging modalities which propose the measurement of
 stiffness parameters. Circumferential stiffness (with TTE or MRI) can be evaluated by
 measuring the distensibility. In addition, longitudinal stiffness can be evaluated by
 measuring the local PWV.

 We aim at better defining the vascular involvement of BAV patients by determining the
 prognostic role of functional parameters as non-invasive predictive factors for aortic
 dilation.

 Hypothesis:

 1.Main hypothesis The main hypothesis is that the progression of aortic dilation is dependent
 on the longitudinal and circumferential aortic stiffness in case of BAV.

 The investigators will therefore try to demonstrate a correlation between the local PWV
 measurements in MRI, combined with a simultaneous measurement of the non-invasive central
 pressure (SphygmoCor XCEL®, Atcor Medical ©), with the segmental aortic size progression. The
 investigators hope to define new biomarkers aortic dilation prediction.

 1.Secondary hypothesis

 -  The measurement of the local PWV of the common carotid artery, measured with UF, is
 correlated with the progression of the aortic dilation.

 -  The measurement of aortic distensibility at the Valsalva sinus and ascending tubular
 aortic levels, measured in TTE or MRI, correlates with the progression of aortic
 dilation.

 Originality and innovative aspects - Prospective evaluation of the different aortic segments
 dilatation in case of BAV: Few studies have prospectively evaluated the aortic dilation
 progression in BAV. There are currently no prognostic markers of dilatation validated in this
 group.

 - Use of aortic MRI combined with central pressure measurement as a prognostic evaluation
 tool for aortopathy associated with BAV: Following the development of 4D MRI in
 cardiovascular imaging, evaluation of the aorta is possible by studying both the wall's
 movements during the cardiac cycle and the wall shear stress evaluation. This makes possible
 to obtain, at each part of the thoracic aorta, measures of circumferential distensibility,
 local PWV, and shear stress.

 Coupling these two imaging modalities is particularly interesting in the aortic evaluation of
 BAV due to the involvement of the flow changes in aortic stiffness.

 - Use of the common carotid artery stiffness as a prognostic evaluation tool for aortopathy
 associated with BAV independently of the aortic diameter Due to the common embryological
 origin of aorta and the common carotid arteries, aortopathy associated with BAV is associated
 with an increase in of the common carotid arteries stiffness.

 The evaluation of the carotid artery will therefore help to evaluate the correlation between
 carotid rigidity and progression of aortic dilation.

 - Evaluation of the local PWV as carotid stiffness biomarker Ultrasound analysis will also be
 innovative, with the use of a fine ultrasonic method with very high frame rate (more than
 10,000 images per second) developed by the Langevin Institute (Mathias Fink, Michael Tanter
 and Mathieu Pernot). The collaboration between the Langevin Institute and the H.E.G. lead to
 numerous publications both in the vascular and cardiac levels. The vascular medicine
 department has an Aixplorer® prototype with vascular and cardiac applications on site. The
 advantage of this technology is its ultrafastecho mode with very high temporal resolution
 which allows the vascular level to visualize and to calculate the speed of the arterial pulse
 wave which is correlated to the local rigidity.

 The use of this innovative technique in aortic bicuspid will hopefully validate the
 evaluation of the carotid velocity of the pulse wave as an easily accessible prognostic
 marker of aortic dilation.

 Purpose of the research

 The objective is the development and validation of morphological markers informative of
 aortic dilatation in order to improve the precision of the risk of aneurysm of the thoracic
 aorta and of acute aortic syndrome for patients with BAV.

 The primary objective of this study is to demonstrate a correlation between the aortic local
 PWV measured with MRI and the progression of the thoracic aorta diameters measured by MRI
 after a follow-up of 2 years

 The secondary objectives are:

 1. To demonstrate a correlation between the progression of the dilatation of the different
 segments of the thoracic aorta with the following measures:

 -  Aortic distensibility measured in MRI at the Valsalva sinus and at the ascending
 tubular aortic level.

 -  Aortic distensibility measured in TTE of the same segments in TM and in B mode .

 -  Carotid pulse rate measured on carotid arteries by UF.

 2. To demonstrate a correlation between the progression of the dilatation of the different
 segments of the thoracic aorta with the following environmental risk factors:

 -  Active Smoking

 -  Diabetes

 -  Hypertension

 -  Familial form of aortic BAV (defined by the presence of a relative, 1st or 2nd
 degree, with BAV or thoracic aortic aneurysm)

 -  Morphological type of BAV

 -  Aortic coarctation
Inclusion Criteria:

 -  Adults over 18 years of age,

 -  confirmed BAV by TTE computed tomography or MRI.

 -  Adults benefiting from a social security scheme,

 -  having received information on the research

 -  having signed the consent form

 Exclusion Criteria:

 -  Patient with a syndromic form of BAV:

 -  Loeys-Dietz syndrome,

 -  Turner syndrome

 -  Williams-Beuren syndrome

 -  Shone syndrome