Haemodynamic stress in lateral saccular aneurysms

Abstract

The flow velocities in lateral glass and silastic aneurysm models were quantitatively measured with the non-invasive laser Doppler method. The influences of the elasticity of the wall, the pulse wave and the properties of the perfusion medium on the intra-aneurysmal circulation were investigated. As shown previously, the inflow into the aneurysm arose from the downstream lip and was directed toward the centre of the fundus. Backflow to the parent vessel took place along the walls of the fundus. With non-pulsatile perfusion, flow velocities in the centre of the standardized aneurysms varied between 0.4 and 2% of the maximum velocity in the parent vessel. With pulsatile perfusion, flow velocities in the centre of the fundus ranged between 8 and 13% of the flow velocity in the axis of the parent vessel. Flow velocities in the aneurysms were slower with a macromolecular perfusion medium with blood like properties compared to a glycerol/water solution. Flow velocity measurements near the aneurysmal wall allowed the estimation of the shear stresses at critical locations. The maximum shear stresses at the downstream lip of the aneurysm were in the range of the stresses measured at the flow divider of an arterial bifurcation. The present results suggest that in human saccular aneurysms intra-aneurysmal flow and shear stress on the wall are directly related to the pulsatility of perfusion, i.e. the systolic/diastolic pressure difference and that the tendency to spontaneous thrombosis depends on the viscoelastic properties of the blood, namely the haematocrit.

Numerical and experimental studies on pulsatile flow in aneurysms arising laterally from a curved parent vessel at various angles

“…On the other hand, all values of g have the highest t w =ðrU 2 max Þ occurring around the distal orifice lip. This observation is similar to that of Steiger et al (1987) and of Lo¨w et al (1993) in their rigid or elastic lateral aneurysm models of g ¼ 0 . Suzuki and Ohara (1978) in their in vivo investigation pointed out that the blood flow often leads to the orifice wall reinforced by proliferation of intima.…”

In Vitro Measurement of Fluid-Induced Wall Shear Stress in Unruptured Cerebral Aneurysms Harboring Blebs

“…A previous in vitro study demonstrated that there was no remarkable difference in flow characteristics between rigid and elastic aneurysm models. 34 Given the difficulty of accurate measurement of shearing velocity on a moving wall, reasonable flow simulation can be performed with rigid aneurysm models. This experimental model allows the comparison of the wall shear stress profile with the morphology, geometric disposition, location, and natural history of aneurysms.…”

Vascular Dynamics of a Shape Memory Polymer Foam Aneurysm Treatment Technique

“…Ferguson 26 compared the elasticity of aneurysms to that of major intrancranial arteries and observed that aneurysms are relatively indistensible, indicating a loss of elastin within their walls. The in vitro experiments of Steiger et al 70 on lateral, saccular aneurysms demonstrated that the flow within an aneurysm is much more sensitive to the pulsatile nature of the cardiac waveform than to the effects of vessel wall deformation. Additionally, others 23,60,83 showed that although wall elasticity slightly decreases the magnitude of the wall shear stress, the overall flow and stress patterns within the vessel remain unchanged.…”