Steady flow and wall compression in stenotic arteries: a three-dimensional thick-wall model with fluid-wall interactions

Computational modeling of vascular anastomoses

Recent development of computational technology allows a level of knowledge of biomechanical factors in the healthy or pathological cardiovascular system that was unthinkable a few years ago. In particular, computational fluid dynamics (CFD) and computational structural (CS) analyses have been used to evaluate specific quantities, such as fluid and wall stresses and strains, which are very difficult to measure in vivo. Indeed, CFD and CS offer much more variability and resolution than in vitro and in vivo methods, yet computations must be validated by careful comparison with experimental and clinical data. The enormous parallel development of clinical imaging such as magnetic resonance or computed tomography opens a new way toward a detailed patient-specific description of the actual hemodynamics and structural behavior of living tissues. Coupling of CFD/CS and clinical images is becoming a standard evaluation that is expected to become part of the clinical practice in the diagnosis and in the surgical planning in advanced medical centers. This review focuses on computational studies of fluid and structural dynamics of a number of vascular anastomoses: the coronary bypass graft anastomoses, the arterial peripheral anastomoses, the arterio-venous graft anastomoses and the vascular anastomoses performed in the correction of congenital heart diseases.

Ultrasound image-based computer model of a common carotid artery with a plaque

Ultrasound scans were acquired from a common carotid artery in a patient with an early atherosclerotic plaque forming a mild asymmetrical stenosis. The 3D vascular geometry of the diseased arterial segment was reconstructed from a series of 2D cross-sectional images, and computational meshes for the flow and wall domains were developed. Numerical flow simulations incorporating coupled fluid-solid interaction were implemented using flow and pressure waveforms measured in vivo. The effects of wall distensibility were investigated by comparing the predictions obtained with different wall compliance, one with 'natural' compliance and another with a stiffer wall. Limited flow separation was predicted in the post-stenotic zone. The non-uniform thickness of the diseased wall restricted the wall motion locally and re-distributed the stress, giving raised concentrations at the plaque shoulders.

Effect of a lipid pool on stress/strain distributions in stenotic arteries: 3-D fluid-structure interactions (FSI) models

Nonlinear 3-D models with fluid-structure interactions (FSI) based on in vitro experiments are introduced and solved by ADINA to perform flow and stress/strain analysis for stenotic arteries with lipid cores. Navier-Stokes equations are used as the governing equations for the fluid. Hyperelastic Mooney-Rivlin models are used for both the arteries and lipid cores. Our results indicate that critical plaque stress/strain conditions are affected considerably by stenosis severity, eccentricity, lipid pool size, shape and position, plaque cap thickness, axial stretch, pressure, and fluid-structure interactions, and may be used for possible plaque rupture predictions.

Blood vessel constitutive models-1995-2002

Knowledge of blood vessel mechanical properties is fundamental to the understanding of vascular function in health and disease. Analytic results can help physicians in the clinic, both in designing and in choosing appropriate therapies. Understanding the mechanical response of blood vessels to physiologic loads is necessary before ideal therapeutic solutions can be realized. For this reason, blood vessel constitutive models are needed. This article provides a critical review of recent blood vessel constitutive models, starting with a brief overview of the structure and function of arteries and veins, followed by a discussion of experimental techniques used in the characterization of material properties. Current models are classified by type, including pseudoelastic, randomly elastic, poroelastic, and viscoelastic. Comparisons are presented between the various models and existing experimental data. Applications of blood vessel constitutive models are also briefly presented, followed by the identification of future directions in research.

Hemodynamics of Carotid Artery Atherosclerotic Occlusive Disease

Hemodynamic mechanisms for the initiation and progression of carotid bifurcation atherosclerotic occlusive disease have been extensively researched during the past few decades. Attention has focused on the carotid bulb, or sinus, where most atherosclerotic plaques are found. Herein, the authors review the seminal works that have led to an understanding of not only complex local hemodynamics but also the elicited specific biologic response. In addition, new analysis of the age-dependent morphologic maturation of the human carotid bifurcation is unveiled. Understanding the role of hemodynamics in atherogenesis may lead to the improvement of minimally invasive endovascular therapy and noninvasive strategies.