Role of Computational Fluid Dynamics in the Analysis of Haemodynamic and Morphological Characteristics of Intracranial Aneurysms

Aneurysmal subarachnoid hemorrhage (SAH) carries a high morbidity and mortality. The current protocols used to treat the unruptured Intracranial Aneurysms (IAs) are inadequate underscoring the need of finding new descriptors. As demonstrated by the studies performed in this manuscript, haemodynamics plays an important role in the aetiopathogenesis of IAs. An evaluation of haemodynamic indices can provide a useful alternative to predict the behavior of an unruptured IA at an early stage. Studies performed by me demonstrate that Computational Fluid Dynamics (CFD) can be used successfully to predict haemodynamic indices where detailed in vivo measurement of haemodynamic flow variables is not possible owing to technical limitations. European Commission funded Project @neurIST was the first project of it’s kind that brought together a number of multidisciplinary professionals from 32 European institutions and made possible development of state-of-the-art tools for personalised risk assessment and treatment IAs using CFD. These tools have been constantly improved and amended in the light of feedback gathered from their controlled exposures conducted world over, as described in the manuscript. However, need of a well-designed Randomized Controlled Trial in this context cannot be overemphasized, before these tools can be accepted by clinicians and patients. In my study on the validation of different concepts used in CFD, I demonstrated that there is no added advantage of complex Womersley-flow-profile over the much simpler plug-flow profile. One of my studies on initiation and rupture of IAs showed that the haemodynamic patterns of IAs during these two phases are significantly different with values of supra-physiological Wall Shear Stress (WSS) being higher in initiation while lower in rupture phase. I also investigated the effects of pharmacological agents on the aetiopathogenesis of IAs and found that heparin induces significant derangements in the haemodynamics of both, pre-aneurysmal as well as ruptured IA. I propose that heparin (and its derivatives) can, on the one hand may facilitate the rupture of existing IAs, on the other hand they may suppress the formation of new IAs. I have also found significant differences in the results using patient-specific vs. Modeled Boundary Conditions and showed that the 1D circulation model adopted by @neurIST performs better than other approaches found in the literature. I also proposed a novel mechanism of increase in Blood Viscosity leading to high WSS as one of the important underlying mechanisms responsible for the increased incidence of IA formation in smokers and hypertensive patients. In my study on patients with pre-existing Coarctation of Aorta (CoA) and Intracranial Aneurysms, I demonstrated that the cerebral flow-rates in CoA patients were significantly higher when compared to average flow-rates in healthy population. It was also seen that the values and the area affected by supraphysiological WSS (>15Pa) were exponentially higher in patients with CoA indicating the possible role of increased haemodynamic WSS secondary to the increased flow-rates playing an important role in the pathogenesis and rupture of IAs in CoA patients.