Flow studies in glass models of aortic aneurysms

A photodensitometer was used to make a quantitative analysis of flow into and out of glass models of three types of aortic aneurysm (small and large fusiform and small saccular). The "aneurysms" were perfused with steady flow and injected with Evans' blue dye. The aneurysms tended to fill linearly with time, but emptied exponentially. Flow out of both large and small fusiform aneurysms did not alter as a function of the Reynolds number (a nondimensional measurement used to compare flows in tubes of the same shape but of different sizes), while flow from the saccular aneurysm did. The results suggest that the flow in fusiform aneurysms is very sluggish. This may increase the risk of thrombosis and could also lead to a false arteriographic analysis of size, particularly in large aneurysms. Emptying of saccular aneurysms is much more dependent on the Reynolds number and hence on location and blood viscosity.