Onset and nature of flow-induced vibrations in cerebral aneurysms via fluid-structure interaction simulations

Clinical, experimental, and recent computational studies have demonstrated the presence of wall vibrations in cerebral aneurysms, thought to be induced by blood flow instability. These vibrations could induce irregular, high-rate deformation of the aneurysm wall, and potentially disrupt regular cell behavior and promote deleterious wall remodeling. In order to elucidate, for the first time, the onset and nature of such flow-induced vibrations, in this study we imposed a linearly increasing flow rate on high-fidelity fluid-structure interaction models of three anatomically realistic aneurysm geometries. Prominent narrow-band vibrations in the range of 100-500 Hz were found in two out of the three aneurysm geometries tested, while the case that did not exhibit flow instability did not vibrate. Aneurysm vibrations consisted mostly of fundamental modes of the entire aneurysm sac, with the vibrations exhibiting more frequency content at higher frequencies than the flow instabilities driving those vibrations. The largest vibrations occurred in the case which exhibited strongly banded fluid frequency content, and the vibration amplitude was highest when the strongest fluid frequency band was an integer multiple of one of the natural frequencies of the aneurysm sac. Lower levels of vibration occurred in the case which exhibited turbulent-like flow with no distinct frequency bands. The current study provides a plausible mechanistic explanation for the high-frequency sounds observed in cerebral aneurysms, and suggests that narrow-band (vortex-shedding type) flow might stimulate the wall more, or at least at lower flow rates, than broad-band, turbulent-like flow.

Automated summary

Clinical, experimental, and computational studies have found that vibrations in cerebral aneurysms induced by blood flow instability could lead to wall deformation and cell behavior disruption. This study imposed increasing flow rates on realistic aneurysm models and observed narrow-band vibrations in two out of three geometries tested, with the strongest vibrations occurring when the fluid frequency band matched one of the aneurysm sac's natural frequencies. The study provides a potential mechanistic explanation for the high-frequency sounds in cerebral aneurysms and suggests that narrow-band flow might stimulate the aneurysm wall more effectively than broad-band, turbulent-like flow.