Computational models to predict stenosis growth in carotid arteries: Which is the role of boundary conditions?

Abstract

This work addresses the problem of prescribing proper boundary conditions at the artificial boundaries that separate the vascular district from the remaining part of the circulatory system. A multiscale (MS) approach is used where the Navier-Stokes equations for the district of interest are coupled to a non-linear system of ordinary differential equations which describe the circulatory system. This technique is applied to three 3D models of a carotid bifurcation with increasing stenosis resembling three phases of a plaque growth. The results of the MS simulations are compared to those obtained by two stand-alone models. The MS shows a great flexibility in numerically predicting the haemodynamic changes due to the presence of a stenosis. Nonetheless, the results are not significantly different from a stand-alone approach where flows derived by the MS without stenosis are imposed. This is a consequence of the dominant role played by the outside districts with respect to the stenosis resistance.

Geometric multiscale modeling of the cardiovascular system, between theory and practice

“…In this respect, we mention [106,107,121] applied to the Total Cavopulmonary Connection obtained as a therapy for Left Ventricle Hypoplasia Syndrome and [12] for the analysis of carotid stenosis. In the latter paper, an extensive comparison of different boundary conditions in both stand-alone and multiscale settings is carried out, pointing out the importance of the combination of local/systemic perspectives granted by multiscale coupling for the reliability of numerical simulations.…”

“…A detailed description of the venous system of the head and neck is obtained by reconstructing 3D geometries with the software VMTK [4] and successively extracting the centerlines to build the related 1D network. The wall law is given by (12), with different values of n 1 and n 2 depending on the district considered. Vein valves are modeled with diodes.…”

A numerical investigation of the functionality of coronary bifurcation lesions with respect to lesion configuration and stenosis severity

“…Although studies have suggested that blood flow can transition from a laminar to turbulent regime in stenosed vessels (Mallinger and Drikakis, 2002;Sherwin and Blackburn, 2005), laminar flow was assumed in order to simplify numerics (Balossino et al, 2009) and justified based on the fact that the peak inlet Reynolds number (Re peak ) did not significantly surpass the suggested threshold of 500 (Re peak,max E590 for the (0,0,0) configurations with 41% stenoses, Re peak,max E565 for multilesional configurations with 50% stenoses). The vessel walls were taken to be rigid, which is a reasonable assumption for diseased coronary vessels which experience peak circumferential strains below 5% (Kelle et al, 2011).…”

“…Instead, patient-specific models are coupled to 0D patient-tailored models of surrounding cardiovascular domains, Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com allowing for boundary flows and pressures to be determined through the interaction of the two models. Although work is ongoing regarding the optimization of multiscale models (Pant et al, 2014), their use is becoming more prominent; they have been implemented for various applications including disease progression (Balossino et al, 2009), and modelling/optimization of surgical/ interventional procedures (Lagana et al, 2005;Moghadam et al, 2012;Morlacchi et al, 2011). For isolated lesions, the onset of ischemia is influenced by various factors including lesion morphology and location, the size and dynamics of the perfused myocardium and the extent of collateral circulation (Pijls and Sels, 2012;Yong et al, 2011).…”

Imaging and patient-specific simulations for the Fontan surgery: Current methodologies and clinical applications

“…Recent advances in boundary condition methods for cardiovascular simulations have enabled simulations to achieve physiologic levels of pressure that can reproduce pressure levels and time-varying pressure fluctuations obtained via cardiac catheterization(Vignon-Clementel, Figueroa et al 2006; Marsden, Vignon-Clementel et al 2007; Balossino, Pennati et al 2009; Marsden, Reddy et al 2010). This is essential for accurate prediction of flow splits with multiple pulmonary branches, wave propagation, and vessel wall deformability.…”