Resolving high frequency fluctuations in cerebral aneurysm hemodynamics: the critical role of high-fidelity simulations and heart rate effects

Background and Objective Despite their assumed laminar flow conditions, intracranial aneurysm (IA) hemodynamics can exhibit high frequency fluctuations, which recent studies have related to rupture risk. However, accurate detection of these fluctuations is challenging. Therefore, investigation of low and highly resolved numerical simulations to identify increased blood flow frequencies is fundamental for enhancing rupture risk assessments. Methods Highly resolved direct numerical simulations (DNS) and lower-resolution numerical simulations (LRNS) were conducted to assess IA hemodynamics under three representative heart rate frequencies in a patient-specific IA model (HR1: 60 bpm, HR2: 100 bpm, HR3: 137 bpm). The simulated flow fields were validated against particle tracking velocimetry. Flow instabilities were quantified by the power spectral density. Results The velocity fields obtained from both numerical approaches closely matched experimental data (mean v_norm=1 m/s at similar plane through IA). However, LRNS failed to capture intra-aneurysmal vorticity structures, whereas DNS successfully reproduced experimentally observed vorticity patterns. Both methods showed comparable root mean square values and time-resolved probe-wise results (highest differences: ∆0.08 m/s (HR1), ∆0.09 m/s (HR2-3). Conclusions DNS uniquely identified high frequency fluctuations in velocity detected with power spectral density. These fluctuations strengthened with increasing heart rates and were not captured by LRNS. Thus, it is suggested to consider high-fidelity setups when addressing IA rupture risk assessment.