Aortic Dissection (AD) is a pathological situation in which the inner layer of the vessel's tears, causing separation between the inner and middle layers of the aorta. Blood surges into the tears, resulting in vulnerable secondary blood flow channel. Surgery consists in positioning a stent graft in the damaged area to reinforce vessel walls and redirect flow. Tears, surgical tool insertion and stent graft positioning generate flow field disturbances that may influence the evolution of the disease. Understanding of flow disturbances in AA under healthy, dissection and post-surgical conditions would improve surgical planning and success rate.

An experimental study was carried out to assess blood flows in a bio-faithful reproduction of a healthy abdominal aorta (AA). Physiological pulsatile flow rates, non-Newtonian viscoelastic blood properties were replicated in a compliant experimental model of the abdominal aorta. Particularly instationarity cyclic flow involves during AD are recovered from monitored pump. The induced flow rates were investigated performing Particle Image Velocimetry (PIV) in the AA model. These measurements allowed to draw flow fields in the AA model during replicated cardiac cycles under resting conditions (those of AD operation).

Experiments were conducted on a compliant silicon model of an abdominal aorta extended to iliac arteries. The model was shaped based on patient abdominal MRI. An helical pump and a proportional solenoid valve controlled by NI/LabView regulate the flow rate and ensure its pulsatile behaviour. Pressure and flow rate are both monitored upstream and downstream the model via pressure and flow rate captors.

In order to approach blood rheology, a non-Newtonian blood mimicking fluid was obtained as a fluid solution between Xanthan gum and glycerol solutions. This allows to obtain mainly the shear thinning properties necessary to micmic blood.

Fluorescent solid particles of 10 microns size are added to the fluid. Enlightment was obtained via a Lavision system with a pulsed Nd-YAG laser sheet (Nano L120-20 PIV, 532 nm, Litron Lasers). A sCMOS camera was used to captured particle positions at different instants. The AA model is immersed in a tank containing same fluid solution as the fluid flow to prevent light distortion.

In this work the pulsatile flow was successfully replicated in the AA compliant model with respect to flow rates and blood properties. Flow field evolution along cycles will be shown for different locations along the model without tools for surgery. This will be compared with the results obtained with the presence of tool surgery. Global modification of the pressure and pressure drop will be compared with captors' measurements. First attempt to obtain simultaneously the wall aorta deformation during the different cases will be reported.

This work is granted by Auvergne Rhône-Alpes Region, Pack Ambition Recherche Program : @NEDA (Analyse et traitement Numérico-Expérimental de la Dissection Aortique).