In vitro study of haemodynamics in a giant saccular aneurysm model: influence of flow dynamics in the parent vessel and effects of coil embolisation.

The purpose of this study was to investigate the influence of flow dynamics in the parent vessel and of intra-aneurysmal coil embolisation on flow pattern and pressure in an in vitro model of giant aneurysm. A pulsatile perfusion with a glycerol aqueous solution was installed in a silicone model of a lateral giant aneurysm. Flow visualization and pressure measurements were performed while modifying the flow rate, the pulsatility and the pulse rate in the parent vessel, and after partial coil embolisation. Vortices were formed during systole at the downstream lip of the aneurysm and circulated around the aneurysm. The centre and dome of the aneurysm were areas of fluid stagnation. Flow rate and pulsatility were the main factors which varied the pattern of flow within the aneurysm. Partial coil embolisation induced major flow disturbances in the aneurysm, in particular fluid stagnation at the dome. Pressure measurements were similar in the aneurysm and in the parent vessel. It was concluded that the pulsatility of flow is an important as the flow rate when considering the haemodynamics in a giant aneurysm. In the clinical context, this could explain the efficacy of vertebral artery occlusion in thrombosing giant vertebrobasilar aneurysms. Studies with intra-aneurysmal coil embolisation showed early fluid stagnation at the dome. This could result in embolic migration during endovascular treatment. Partial coil embolisation may prevent early rebleeding; however, it may induce additional mural stresses resulting from new haemodynamic forces and compliance mismatch.