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Biomechanical Approach to Improve the Abdominal Aortic Aneurysm (AAA) Rupture Risk Prediction

© 2012 Vilalta et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Biomechanical Approach to Improve the Abdominal Aortic Aneurysm (AAA) Rupture Risk Prediction

Preliminary Correlations for Characterizing the Morphology of Abdominal Aortic Aneurysms as Predictor of Rupture

The morphology of abdominal aortic aneurysms (AAA) has been recognized as a factor that may predispose their rupture. The time variation of the AAA morphology induces hemodynamic changes in morphological behavior that, in turn, alters the distribution of hemodynamic stress on the arterial wall. This behavior can influence the phenomenon of rupture. In order to evaluate the relationship between the main geometric parameters characterizing the AAA and the hemodynamic stresses, 6 AAA models were reconstructed and characterized. The models were characterized using thirteen geometrical factors based on the lumen center line: eight 1D indices, three 3D indices, and two 0D indices. The temporal and spatial distributions of hemodynamic stresses were computed using computational fluid dynamics. The results showed that the hemodynamic stresses are modified by the time variations of the AAA morphology, and therefore, the hemodynamic stresses, in combination with other parameters, could be a criterion for improved rupture risk prediction. Statistical correlations between hemodynamic stresses and geometric indices have confirmed the influence by the AAA morphometry on the prediction of the rupture risks, although higher reliability of these correlations is required.

ABDOMINAL AORTIC ANEURYSM (AAA) MORPHOLOGY AS PREDICTOR OF PEAK WALL STRESS

Taking into account the physical principle of the AAA rupture, recent findings have postulated that aneurysm peak wall stress (PWS) may be superior to diameter in predicting the AAA rupture potential. AAA morphology has strong influence on wall stress distribution. Hence, the aneurysm geometric characterization may be useful in defining some biomechanical predictors to assess AAA rupture severity. Aim of this study was to investigate whether a relation existed between the main geometric parameters of idealized AAAs (simple parameters and GBDs) and PWS values.

HEMODYNAMIC FEATURES ASSOCIATED WITH ABDOMINAL AORTIC ANEURYSM (AAA) GEOMETRY

Recent findings have shown that maximum diameter of abdominal aortic aneurysm (AAA) and its growth rate are not entirely reliable indicators of rupture potential. The AAA geometrical shape and size may be related to the rupture risk which is a clinical manifestation of the balance between the forces generated by blood flow within the AAA and its strength. This study aims at assessing the hemodynamic features associated with the geometry of AAAs.

Modificaciones Hemodinámicas Asociadas a la Asimetría de Aneurismas de Aorta Abdominal y su Influencia en las Posibilidades de Ruptura

Influence of abdominal aortic aneurysms asymmetry on the hemodynamics within the aneurysmatic sac is analyzed and its influence on the rupture potential is discussed. A numerical study by using four idealized geometric models, with different asymmetry degrees, is carried out. Blood is modelled as a newtonian, homogeneous, incompressible and laminar flow with properties as typically used in the literature. The results showed that the flow inside of the aneurysmatic sac is highly disturbed with intense vortex structures travelling from proximal to distal ends, strongly influencing on the wall shear stress distribution. It have also been established that, despite that the aneurysm are asymmetric, this factor has low weight on aneurysm rupture.