Hemodynamic assessment of severely stenotic carotid arteries

A ruptured intracranial aneurysm is a serious life-threatening medical condition. Bleed in the cerebral circulation causes subarachnoid hemorrhage, which is known as hemorrhagic stroke. The present study investigates cerebral blood circulation and aneurysm bleed using the principle of fluid mechanics. Ruptured wide-neck aneurysms are difficult to treat either by surgical clipping or stent-assisted coiling in the acute phase of rupture. Quick and intentional partial coiling (IPC) around the aneurysm rupture region is preferred for an immediate cessation of rebleed after rupture. Furthermore, the stent-assisted complete coiling (SACC) may be performed once the patient is stable and able to withstand the antiplatelet therapy at a later stage. The aneurysm recurrence and rupture after the treatment are the major issues associated with the treatment of a wide-necked aneurysm. The present study analyzes the hemodynamics of IPC followed by SACC using a novel multi-domain porous medium approach. Simulations are performed assuming a hypothesized rupture spot for the aneurysm using flow features and hemodynamic parameters. The optimal coil packing density (PD) required to fill the vicinity of the ruptured spot to prevent early rebleed and facilitate aneurysm occlusion is numerically determined. It is observed that partial coiling requires higher packing density (PD > 30%) than complete coiling to reduce the chances of aneurysm recurrence after the treatment. The insertion of the stent does not affect the aneurysm hemodynamics significantly. The stent-assisted complete coiling requires more than 20% PD to enhance the long-term stability of the treatment.

Hemodynamic investigation of hemorrhagic stroke treatment options for a patient-specific aneurysm using a porous medium model

Panneerselvam,

Akade,

Kumar

et al. 2024

Assessing the impact of fetal-type posterior cerebral artery variations on cerebral hemodynamics

Le,

Ryu,

Yoon

et al. 2024

The circle of Willis (CoW) is a critical, arterial structure that ensures balanced, cerebral-blood supply. The fetal-type posterior cerebral artery (f-PCA) is a CoW variant that can significantly affect hemodynamics and elevate the risk of cerebrovascular diseases. This study used computational fluid dynamics simulations and a patient-specific, three-dimensional model to evaluate the hemodynamic effects of the f-PCA variants on cerebral-blood flow and key hemodynamic indices—such as time-averaged wall-shear stress (TAWSS), oscillatory shear index (OSI), pulsatility index, and resistive index. The fetal ratio (FR) is defined as the ratio of the diameter of the posterior communicating artery (PCoA) to that of the first segment (P1) of the PCA. Our findings indicate that as the FR increases, the contribution of the basilar artery to the second segment (P2) of PCA decreases significantly. Specifically, the flow rate through ipsilateral P1 decreased by 40.0% for FR = 1 and 70.9% for FR = 2, with the internal carotid artery (ICA) compensating for this reduction. Moreover, variations in f-PCA led to significant increases in TAWSS and OSI in key arterial segments (including the ipsilateral P1, PCoA, and the anterior communicating artery), which are associated with a higher risk of aneurysm initiation and growth. Under conditions of unilateral stenosis in the ipsilateral ICA, f-PCA models exhibit a more complex and pronounced impact on blood flow than models without f-PCA, emphasizing the need for detailed hemodynamic assessments in clinical evaluations and preoperative planning to mitigate the risks associated with CoW anatomical variations.

Computational fluid dynamics analysis of bypass surgery for a giant internal carotid artery aneurysm

Panchal,

Scaria,

Matham

et al. 2024

Giant intracranial aneurysms are complex and associated with a greater risk of rupture than smaller aneurysms, requiring unique and patient-specific surgical solutions. A giant terminal internal carotid artery aneurysm was surgically managed by a vascular bypass between the internal maxillary artery and the middle cerebral artery using a radial artery graft. This bypass enabled blood flow through the external carotid artery (ECA), as the internal carotid artery was ligated. The present study performs a computational fluid dynamics based assessment of the hemodynamic factors resulting in a successful outcome. The flow domain of interest is extracted from the computed tomography-angio images at two different intervals—before the surgery and after the surgery at t=3 months. An intermediate stage is constructed to reflect the immediate post-surgery (t=0) situation. Numerical simulations are performed using OpenFOAM solver for the non-Newtonian and patient-specific in-flow conditions. Different hemodynamic indicators such as time-averaged magnitude of wall shear stress (|WSS|¯), oscillatory shear index (OSI), and relative residence time (RRT) are derived from the spatiotemporal velocity and pressure data. After the bypass surgery at t=0, the flow facilitated through ECA resulted in a reduction of |WSS|¯ compared to the pre-surgery. Post-surgery (t=0), the region of low |WSS|¯ and high RRT is observed to be responsible for the thrombosis of the aneurysm. Moreover, the present simulation suggests that after three months of surgery, an improvement in values of |WSS|¯ and the reduction in variation of OSI exemplify hemodynamic stability.