Informatics in Medicine Unlocked (Jan 2022)
A study on the computational hemodynamic and mechanical parameters for understanding intracranial aneurysms of patients with hypertension and atrial fibrillation
Abstract
Objective: Intracranial aneurysms of patients with comorbidities like hypertension and atrial fibrillation have elevated rupture risk. Besides, the height and width of the aneurysm sacs are also essential features for pre-operative planning. However, clinicians still use only medical images and aspect ratios to identify which aneurysm has a higher risk of rupture. The rupture risk assessment often remains incomplete for lack of crucial insights. Therefore, the implication of a computational study on aneurysm diagnosis is analyzed in this study. Method: Here, the two-way fluid-structure interaction method is used to reproduce these effects of clinical conditions and geometry on aneurysms. Wall shear stress, oscillatory shear index, total deformation, and other parameters are calculated. Results: The wall shear stress (WSS) is the stress exerted by the wall on the fluid in a direction on the local tangent plane. The WSS inside a larger aneurysm decreases by around 50% compared to the aneurysms with a lower aspect ratio, indicating higher potential growth and rupture risk. However, the maximum pressure during systole for the aneurysm with the highest aspect ratio is 33% lower than the second-largest one during atrial fibrillation because of its unusual geometry. Although these hemodynamic parameters can be used to identify the effects of the size and shape of the aneurysms, they cannot completely depict the impact of the medical conditions. On the other hand, structural parameters like effective stress and total deformation successfully show the influence of size, hypertension, and atrial fibrillation on the aneurysm walls. The time-averaged wall deformation for the largest aneurysm is 1.3 and 2 times higher than the medium and smallest aneurysms, respectively. Moreover, compared to the normal condition, the total deformation at the aneurysm sac walls is 4–8% more for atrial fibrillation and 25–33% more for hypertension. A similar observation is made for the time-averaged value of effective stress exerted on the aneurysm walls, another parameter used to assess the rupture risk of aneurysms. Most importantly, these computational results align with previous clinical studies on patients with hypertension and atrial fibrillation. Conclusion: Based on these observations, it is certain that to understand the impact of the comorbidities of the patients with intracranial aneurysms, results obtained from the structural analysis are required alongside hemodynamic parameters.
