[Effect of position with respect to gravitational force on the hydrodynamics of an experimental model of saccular aneurysm].

We wish to confirm the hypothesis that the hydrodynamics of brain aneurysms depend partially on their position, with respect to the force of gravitation, and so developed an experimental model of latex aneurysms, which was subjected to a pulsatile flow. Four different registers were made with an injection of ink and radioisotopes. A physical model was designed which allowed a quantitative analysis of the results and which allows a mathematical analysis of the aneurysm's hydrodynamics. The results suggest that when an aneurysm is oriented against the force of gravity, it has a very low risk of thrombosis, and the scarce turbulence of the flow condition a lower risk of growth and rupture, in comparison with other conditions. The greatest flow turbulence against the wall is found in the aneurysm oriented downwards, that is parallel to the force of gravity. Due to its hydrodynamics, the downwards aneurysm has the highest probability of complication, since it has; a) higher risk of rupture due to the impact of the stream upon the wall and to the turbulence this impact produces, b) a higher risk of thrombosis produced by the circulatory stasis which has a dome. This combination of factors (rupture and thrombosis) allows these aneurysms to grow more than others.