The Aortic Aneurysm is a pathological dilatation of the aorta. Approximately 80% of aortic aneurysms occur between the renal arteries and the aortic bifurcation in the abdominal tract. This disease is the 14th cause of death in United States. Each year in USA, abdominal aortic aneurysm rupture causes 4500 deaths with an additional 1400 deaths resulting from the 45000 prevent rupture procedures.
Rupture prevention consists in the implantation of a stent endograft to protect the vessel wall from the blood induced damage. There are many types of stents with different geometries. Indeed, geometry plays a crucial role in determining the fluid dynamics of the blood flow. Changes of the physiological geometry can generate complex flow patterns close to the aneurysm neck where the stent is fixed to the vessel. Under pulsatile flow conditions, the geometry induced vorticity can lead to an alteration of an important physio-pathologial parameter represented by the wall shear stress (WSS). The alteration of WWS causes an inflammatory response of the endothelial cells with subsequent thrombus formation (and embolization), aneurysm neck dilatation and stent migration.
The complexity of the problem requires strongly inter-disciplinary skills ranging from the clinical and surgical expertise to fluid dynamics understanding of unsteady flows in complex geometries. The aim of the present proposal is to analyse the hemodynamics modifications caused by different geometries, namely the Gore and Nellix prosthesis used in recent years.
The study will be carried out by a research team composed by vascular surgeons and engineers with specific skills in theirs fields. The clinical staff will provide actual geometries of treated abdominal aortic aneurysms, whilst the engineer team will carry out targeted experiments and numerical simulations to investigate the ensuing WSS. The clinical course will be monitored to correlate actual data on patients with their specific hemodynamical simulation.
The emodynamics occurring in real vessels represents a challenge both under the medical point of view and under the physical point of view.
Indeed, the flow occurs in complex geometries which are likely to change from a patient to an other patient. This calls for the acquisition of the real geometries with dedicated radiological techniques.
Moreover the pulsatile flow conditions are crucial in determining the fluid dynamical response of the blood flow.
The availability of actual geometries and actual pressure signals are crucial for designing well targeted experimental devices or numerical simulations where the blood flow can be reproduced under well controlled conditions.
Under this point of view the present project is ambitious and innovative since it aims at integrating in a single team scientists with expertise in the vascular surgery and scientists with well established expertise in experimental and numerical aspects of fluid dynamics.
We believe that the strongly interdisciplinary medical and physical aspects involved in the blood flow in aortic aneurisms calls for a research team with different expertise in the different fields. A crucial point is indeed the possibility to exchange information and data that are usually restricted to specific and sectorial scientific communities. The aim of the present research is
to break these boundaries and let different and complementary expertise available both for the medical and the engineering community.
The present research represents a unique chance to measure and simulate actual aortic aneurisms. Indeed, the results of the experimental and numerical campaign can be compare against the results that the clinical staff is able to measure on actual patients after the implantation of specific stents used during the surgical treatment.