Blood flow dynamics in saccular aneurysm models of the basilar artery.

Blood flow dynamics under physiologically realistic pulsatile conditions plays an important role in the growth, rupture, and surgical treatment of intracranial aneurysms. The temporal and spatial variations of wall pressure and wall shear stress in the aneurysm are hypothesized to be correlated with its continuous expansion and eventual rupture. In addition, the assessment of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils. This paper describes the flow dynamics in two representative models of a terminal aneurysm of the basilar artery under Newtonian and non-Newtonian fluid assumptions, and compares their hemodynamics with that of a healthy basilar artery. Virtual aneurysm models are investigated numerically, with geometric features defined by beta = 0 deg and beta = 23.2 deg, where beta is the tilt angle of the aneurysm dome with respect to the basilar artery. The intra-aneurysmal pulsatile flow shows complex ring vortex structures for beta = 0 deg and single recirculation regions for beta = 23.2 deg during both systole and diastole. The pressure and shear stress on the aneurysm wall exhibit large temporal and spatial variations for both models. When compared to a non-Newtonian fluid, the symmetric aneurysm model (beta = 0 deg) exhibits a more unstable Newtonian flow dynamics, although with a lower peak wall shear stress than the asymmetric model (beta = 23.2 deg). The non-Newtonian fluid assumption yields more stable flows than a Newtonian fluid, for the same inlet flow rate. Both fluid modeling assumptions, however, lead to asymmetric oscillatory flows inside the aneurysm dome.

Flow dynamics in anatomical models of abdominal aortic aneurysms: computational analysis of pulsatile flow.

Blood flow in human arteries is dominated by time-dependent transport phenomena. In particular, in the abdominal segment of the aorta under a patient's average resting conditions, blood exhibits laminar flow patterns that are influenced by secondary flows induced by adjacent branches and in irregular vessel geometries. The flow dynamics becomes more complex when there is a pathological condition that causes changes in the normal structural composition of the vessel wall, for example, in the presence of an aneurysm. An aneurysm is an irreversible dilation of a blood vessel accompanied by weakening of the vessel wall. This work examines the importance of hemodynamics in the characterization of pulsatile blood flow patterns in individual Abdominal Aortic Aneurysm (AAA) models. These patient-specific computational models have been developed for the numerical simulation of the momentum transport equations utilizing the Finite Element Method (FEM) for the spatial and temporal discretization. We characterize pulsatile flow dynamics in AAAs for average resting conditions by means of identifying regions of disturbed flow and quantifying the disturbance by evaluating wall pressure and wall shear stresses at the aneurysm wall.

Flow dynamics in anatomical models of abdominal aortic aneurysms: computational analysis of pulsatile flow / Dinámica del flujo en modelos anatómicos de aneurismas en el segmento abdominal de la aorta: análisis computacional de flujo pulsátil

Blood flow in human arteries is dominated by time-dependent transport phenomena. In particular, in the abdominal segment of the aorta under a patientÆs average resting conditions, blood exhibits laminar flow patterns that are influenced by secondary flows induced byadjacent branches and in irregular vessel geometries. The flow dynamics becomes more complex when there is a pathological condition that causes changes in the normal structural composition of the vessel wall, for example, in the presence of an aneurysm. An aneurysm isan irreversible dilation of a blood vessel accompanied by weakening of the vessel wall. This work examines the importance of hemodynamics in the characterization of pulsatile blood flow patterns in individual Abdominal Aortic Aneurysm (AAA) models. These patientspecificcomputational models have been developed for the numerical simulation of the momentum transport equations utilizing the Finite Element Method (FEM) for the spatial and temporal discretization. We characterize pulsatile flow dynamics in AAAs for average resting conditions by means of identifying regions of disturbed flow and quantifying the disturbance by evaluating wall pressure and wall shear stresses at the aneurysm wall.

El flujo sanguíneo en el sistema cardiovascular humano está dominado por fenómenos de transporte dependientes del tiempo. Bajo condiciones promedio de descanso del paciente, la sangre en el segmento abdominal de la arteria aorta experimenta patrones de flujo laminar, siendo influenciada la dinámica de vórtices por flujos secundarios generados en curvaturas y arterias adyacentes. Esta dinámica de flujo es más compleja cuando el paciente presenta una condición patológica que causa un cambio en la composición estructural normal de la arteria, por ejemplo, en presencia de un aneurisma. En términos generales, un aneurisma representa una dilatación irreversible causada por el debilitamiento de la pared del vaso sanguíneo. Este trabajo examina la importancia de la hemodinámica en la caracterización de patrones de flujo pulsátil sanguíneo en modelos anatómicamente realistas de aneurismas del segmento infrarenal de la arteria aorta abdominal. Estos modelos computacionales son utilizados para la simulación numérica de las ecuaciones de transporte empleando el método de los elementos finitos para la discretización en espacio y tiempo. Hemos caracterizado la dinámica de flujo pulsátil en aneurismas abdominales para condiciones promedio de descanso por medio de la identificación de regiones de flujo perturbado. La quantificación de este tipo de flujo se basa en la evaluación de la presión y los esfuerzos de corte en la pared interna del aneurisma