Modeling of the Acute Effects of Primary Hypertension and Hypotension on the Hemodynamics of Intracranial Aneurysms

Abstract

Hemodynamics is a risk factor in intracranial aneurysms (IA). Hypertension and pharmacologically induced hypotension are common in IA patients. This study investigates how hypertension and hypotension may influence aneurysmal hemodynamics. Images of 23 IAs at typical locations were used to build patient-specific Computational Fluid Dynamics models. The effects of hypotension and hypertension were simulated through boundary conditions by modulating the normotensive flow and pressure waveforms, in turn produced by a 1D systemic vascular model. Aneurysm location and flow pattern types were used to categorize the influence of hypotension and hypertension on relevant flow variables (velocity, pressure and wall shear stress). Results indicate that, compared to other locations, vertebrobasilar aneurysms (VBA) are more sensitive to flow changes. In VBAs, space-averaged velocity at peak systole increased by 30% in hypertension (16-21% in other locations). Flow in VBAs in hypotension decreased by 20% (10-13% in other locations). Momentum-driven hemodynamic types were also more affected by hypotension and hypertension, than shear-driven types. This study shows how patient-specific modeling can be effectively used to identify location-specific flow patterns in a clinically-relevant study, thus reinforcing the role played by modeling technologies in furthering our understanding of cardiovascular disease, and their potential in future healthcare.

Effect of Renin-Angiotensin-Aldosterone System Inhibitors on the Rupture Risk Among Hypertensive Patients With Intracranial Aneurysms

“…17,18 In hypertension, the RAAS has wide-ranging effects on blood pressure regulation through sodium retention, pressure natriuresis, salt sensitivity, vasoconstriction, endothelial dysfunction, and vascular injury. 8,19,20 Given these facts, in addition to the directly increasing hemodynamic stresses, 21,22 activation of the RAAS by systemic hypertension can cause vascular inflammation, injury, and remodeling and thereby contribute to the process of intracranial aneurysm rupture. 9,13 Our study found that RAAS inhibitors decreased the rupture risk of intracranial aneurysms independent of blood pressure control.…”

Wall Mechanical Properties and Hemodynamics of Unruptured Intracranial Aneurysms

“…Our flow conditions were derived from normal subjects and scaled with the patient-specific inflow vessel sizes, but the effects of co-morbidities such as hypertension were not considered. While our assumptions may be reasonable [23], the effects of other co-morbidities should be investigated in future studies. In addition, we considered uniaxial loading, recognizing that in vivo loading is closer to equi-biaxial.…”

Review of in silico models of cerebral blood flow in health and pathology

“…There now exist substantial databases of clinical and imaging data from patients with both ruptured and unruptured aneurysms, for example through the @neurIST project (with nearly 500 patients); for full details of the processing toolchain, see Bogunovic et al (2011) andVilla-Uriol et al (2011). These provide populations from which virtual populations can be reconstructed and studies performed to quantify the effects of parameters such as hypertension and hypotension, Sarrami-Foroushani et al (2015).…”