  Aortic root dilation and propensity to dissection are typical manifestations
of the Marfan Syndrome (MS), a genetic defect leading to the degeneration of
the elastic fibres. Dilation affects the structure of the flow and, in turn,
altered flow may play a role in vessel dilation, generation of aneurysms, and
dissection. The aim of the present work is the investigation in-vitro of the
fluid dynamic modifications occurring as a consequence of the morphological
changes typically induced in the aortic root by MS. A mock-loop reproducing the
left ventricle outflow tract and the aortic root was used to measure time
resolved velocity maps on a longitudinal symmetry plane of the aortic root. Two
dilated model aortas, designed to resemble morphological characteristics
typically observed in MS patients, have been compared to a reference, healthy
geometry. The aortic model was designed to quantitatively reproduce the change
of aortic distensibility caused by MS. Results demonstrate that vorticity
released from the valve leaflets, and possibly accumulating in the root, plays
a fundamental role in redirecting the systolic jet issued from the aortic
valve. The altered systolic flow also determines a different residual flow
during the diastole.
