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In this study, a coupled dimensionally-heterogeneous model of the systemic circulation is applied in order to study computationally the influence of the heart rate in the local hemodynamics. This is achieved by using a 3D-1D-0D model of the whole arterial tree accounting for: details of the local blood flow in the vessel of interest through 3D models, the wave propagation phenomena in the larger arteries by means of 1D models and, the peripheral microvascular beds via 0D models. Two applications are presented which aim at assessing the influence of the global setting of the vascular network on the local hemodynamics. In the first example, the hemodynamics in a patient-specific model of the abdominal aorta is studied for two different systemic scenarios corresponding to different resting heart rates. In the second example, the blood flow in a standardized model of the carotid artery is analyzed for different heart rates including the resting state and several other exercise regimes. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Tortuous vessels are often observed in vivo and could hinder or even disrupt blood flow to distal organs. Besides genetic and biological factors, the in vivo mechanical loading seems to play a role in the formation of tortuous vessels, but the mechanism for formation of helical vessel shape remains unclear. Accordingly, the aim of this study was to investigate the biomechanical loads that trigger the occurrence of helical buckling in blood vessels using finite element analysis. Porcine carotid arteries were modeled as thick‐walled cylindrical tubes using generalized Fung and Holzapfel‐Gasser‐Ogden constitutive models. Physiological loadings, including axial tension, lumen pressure, and axial torque, were applied. Simulations of various geometric dimensions, different constitutive models and at various levels of axial stretch ratios, lumen pressures, and twist angles were performed to identify the mechanical factors that determine the helical stability. Our results demonstrated that axial torsion can cause wringing (twist buckling) that leads to kinking or helical coiling and even looping and winding. The specific buckling patterns depend on the combination of lumen pressure, axial torque, axial tension, and the dimensions of the vessels. This study elucidates the mechanism of how blood vessels buckle under various mechanical loads and how complex mechanical loads yield helical buckling. The novelties of this research article include the following: Illustrated that mechanical loadings such as lumen pressure, axial tension, and axial torque could lead to the formation of tortuous vessels (curving, wringing, kinking, helical coiling, looping, and winding).Determined the biomechanical loads that trigger helical buckling in blood vessels.Compared the effect of different constitutive models. [ABSTRACT FROM AUTHOR]