The changes of flow characteristics caused by a stent in fusiform aneurysm models

Endovascular embolisation technique using a tubular shaped stent is currently used to treat the aneurysm with a wide neck. In order to clarify the hemodynamic changes caused by a stent, the flow fields inside the fusiform aneurysm models were measured using a flow visualization technique incorporating photochromic dye. The flow fields in the non-stented model and those in the stented models with different porosities were compared. A strong inflow motion from the distal neck of aneurysm and a large vortex motion were observed in the non-stented model. Inflow from the distal neck of aneurysm was diminished and sluggish flow inside the aneurysm was observed in the stented models. Wall shear rates were also measured along the aneurysm wall. The shear rates were smaller in the stented models except for the early acceleration phase, and oscillatory shear indices (OSI´s) were higher in the stented models. Since reduced velocity, decreased wall shear rate and increased OSI can promote thrombus formation and intimal hyperplasia, we expect insertion of a stent provide favorable hemodynamic environment for aneurysm embolisation.