Dynamics of pulsatile flow through model abdominal aortic aneurysms

Abstract To contribute to the understanding of flow phenomena in abdominal aortic aneurysms, numerical computations of pulsatile flows through aneurysm models and a stability analysis of these flows were carried out. The volume flow rate waveforms into the aneurysms were based on measurements of these waveforms, under rest and exercise conditions, of patients suffering abdominal aortic aneurysms. The Reynolds number and Womersley number, the dimensionless quantities that characterize the flow, were varied within the physiologically relevant range, and the two geometric quantities that characterize the model aneurysm were varied to assess the influence of the length and maximal diameter of an aneurysm on the details of the flow. The computed flow phenomena and the induced wall shear stress distributions agree well with what was found in PIV measurements by Salsac et al. (J. Fluid Mech., vol. 560, 2006, pp. 19–51). The results suggest that long aneurysms are less pathological than short ones, and that patients with an abdominal aortic aneurysm are better to avoid physical exercise. The pulsatile flows were found to be unstable to three-dimensional disturbances if the aneurysm was sufficiently localized or had a sufficiently large maximal diameter, even for flow conditions during rest. The abdominal aortic aneurysm can be viewed as acting like a ‘wavemaker’ that induces disturbed flow conditions in healthy segments of the arterial system far downstream of the aneurysm; this may be related to the fact that one-fifth of the larger abdominal aortic aneurysms are found to extend into the common iliac arteries. Finally, we report a remarkable sensitivity of the wall shear stress distribution and the growth rate of three-dimensional disturbances to small details of the aneurysm geometry near the proximal end. These findings suggest that a sensitivity analysis is appropriate when a patient-specific computational study is carried out to obtain a quantitative description of the wall shear stress distribution.

[1]  R. Barth,et al.  Ultrasonic evaluation of abdominal aortic thrombus. , 1982, Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine.

[2]  Spencer J. Sherwin,et al.  Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows , 2005, Journal of Fluid Mechanics.

[3]  D. Vorp,et al.  Biomechanics of abdominal aortic aneurysm. , 2007, Journal of biomechanics.

[4]  U. Heinzmann,et al.  Flow mediated fibrin thrombus formation in an endothelium-lined model of arterial branching. , 1994, Thrombosis research.

[5]  Christopher P. Cheng,et al.  Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics , 2011, Annals of Biomedical Engineering.

[6]  T. Hughes,et al.  Effect of exercise on hemodynamic conditions in the abdominal aorta. , 1999, Journal of vascular surgery.

[7]  G. Sheard,et al.  Wall shear stress and flow stability in a model fusiform aneurysm , 2008 .

[8]  Charles A. Taylor,et al.  Quantification of Hemodynamics in Abdominal Aortic Aneurysms During Rest and Exercise Using Magnetic Resonance Imaging and Computational Fluid Dynamics , 2010, Annals of Biomedical Engineering.

[9]  Charles A. Taylor,et al.  Patient-specific modeling of cardiovascular mechanics. , 2009, Annual review of biomedical engineering.

[10]  M. Thompson,et al.  Pulsatile flow in stenotic geometries: flow behaviour and stability , 2009, Journal of Fluid Mechanics.

[11]  S. R. Parks,et al.  Evolution of the wall shear stresses during the progressive enlargement of symmetric abdominal aortic aneurysms , 2006, Journal of Fluid Mechanics.

[12]  J. Bosch,et al.  Epidemiology, aetiology, risk of rupture and treatment of abdominal aortic aneurysms: does sex matter? , 2009, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery.

[13]  E A Finol,et al.  The effect of asymmetry in abdominal aortic aneurysms under physiologically realistic pulsatile flow conditions. , 2003, Journal of biomechanical engineering.

[14]  Yannis Papaharilaou,et al.  Experimental unsteady flow study in a patient-specific abdominal aortic aneurysm model , 2011 .

[15]  M. Thompson,et al.  Subharmonic mechanism of the mode C instability , 2005 .

[16]  V. Deplano,et al.  Flow behaviour in an asymmetric compliant experimental model for abdominal aortic aneurysm. , 2007, Journal of biomechanics.

[17]  Charles A. Taylor,et al.  Intracranial and abdominal aortic aneurysms: similarities, differences, and need for a new class of computational models. , 2008, Annual review of biomedical engineering.

[18]  D A Vorp,et al.  Association of intraluminal thrombus in abdominal aortic aneurysm with local hypoxia and wall weakening. , 2001, Journal of vascular surgery.

[19]  T. Herbert.  Secondary Instability of Boundary Layers , 1988 .

[20]  D. Ku.  BLOOD FLOW IN ARTERIES , 1997 .

[21]  Gregory J. Sheard,et al.  Flow dynamics and wall shear-stress variation in a fusiform aneurysm , 2009 .

[22]  A. Biesheuvel,et al.  Global stability analysis of flow through a fusiform aneurysm: steady flows , 2014, Journal of Fluid Mechanics.

[23]  S. C. Hunley,et al.  Simulation of abdominal aortic aneurysm growth with updating hemodynamic loads using a realistic geometry. , 2011, Medical engineering & physics.

[24]  Charles Taylor,et al.  EXPERIMENTAL AND COMPUTATIONAL METHODS IN CARDIOVASCULAR FLUID MECHANICS , 2004 .

[25]  A. Barakat.  Blood flow and arterial endothelial dysfunction: Mechanisms and implications , 2013 .

[26]  T W Taylor,et al.  Three-dimensional simulation of blood flow in an abdominal aortic aneurysm--steady and unsteady flow cases. , 1994, Journal of biomechanical engineering.

[27]  Timothy J. Pedley,et al.  The fluid mechanics of large blood vessels , 1980 .

[28]  G. Hamilton,et al.  Suggested standards for reporting on arterial aneurysms. , 1992, Journal of vascular surgery.

[29]  M. Armon,et al.  Common iliac artery aneurysms in patients with abdominal aortic aneurysms. , 1998, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery.

[30]  J D Humphrey,et al.  Mechanics, mechanobiology, and modeling of human abdominal aorta and aneurysms. , 2012, Journal of biomechanics.

[31]  Anne-Virginie Salsac,et al.  Hemodynamic Changes Occurring during the Progressive Enlargement of Abdominal Aortic Aneurysms , 2004, Annals of vascular surgery.

[32]  S. Vanka,et al.  THREE-DIMENSIONAL FLOQUET INSTABILITY OF THE WAKE OF SQUARE CYLINDER , 1999 .

[33]  Shichang Shu.  SPACE-LIKE HYPERSURFACES IN LOCALLY SYMMETRIC LORENTZ SPACE , 2008, The ANZIAM Journal.

[34]  J. Lasheras.  The Biomechanics of Arterial Aneurysms , 2007 .

[35]  R. Budwig,et al.  Model studies of the flow in abdominal aortic aneurysms during resting and exercise conditions. , 1999, Journal of biomechanics.

[36]  G. Woodruff,et al.  BLOOD FLOW IN ARTERIES , 2009 .

[37]  S. Yu,et al.  Oscillatory flows in straight tubes with an axisymmetric bulge , 2002 .

[38]  Martin Daniel Griffith.  Stabilité et dynamique des écoulements en géométrie de sténose , 2007 .

[39]  S. C. Yu,et al.  Cyclic transition to turbulence in rigid abdominal aortic aneurysm models , 2001 .