Steady flow in an aneurysm model: correlation between fluid dynamics and blood platelet deposition.

Laminar and turbulent numerical simulations of steady flow in an aneurysm model were carried out over Reynolds numbers ranging from 300 to 3600. The numerical simulations are validated with Digital particle Image Velocimetry (DPIV) measurements, and used to study the fluid dynamic mechanisms that characterize aneurysm deterioration, by correlating them to in vitro blood platelet deposition results. It is shown that the recirculation zone formed inside the aneurysm cavity creates conditions that promote thrombus formation and the viability of rupture. Wall shear stress values in the recirculation zone are around one order of magnitude less than in the entrance zone. The point of reattachment at the distal end of the aneurysm is characterized by a pronounced wall shear stress peak. As the Reynolds number increases in laminar flow, the center of the recirculation region migrates toward the distal end of the aneurysm, increasing the pressure at the reattachment point. Under fully turbulent flow conditions (Re = 3600) the recirculation zone inside the aneurysm shrinks considerably. The wall shear stress values are almost one order of magnitude larger than those for the laminar cases. The fluid dynamics mechanisms inferred from the numerical simulation were correlated with measurements of blood platelet deposition, offering useful explanations for the different morphologies of the platelet deposition curves.

[1]  D. L. Fry.  Acute Vascular Endothelial Changes Associated with Increased Blood Velocity Gradients , 1968, Circulation research.

[2]  K. Perktold.  On the paths of fluid particles in an axisymmetrical aneurysm. , 1987, Journal of biomechanics.

[3]  H. Goldsmith,et al.  Adhesion of human platelets to collagen on the walls distal to a tubular expansion. , 1979, Microvascular research.

[4]  D D Duncan,et al.  Effects of arterial compliance and non-Newtonian rheology on correlations between intimal thickness and wall shear. , 1992, Journal of biomechanical engineering.

[5]  Pressure and flow in arterial aneurysms simulated in mathematical models , 1981 .

[6]  Edward F. Leonard,et al.  Blood in contact with natural and artificial surfaces. , 1988, Annals of the New York Academy of Sciences.

[7]  D. F. Young.  Fluid Mechanics of Arterial Stenoses , 1979 .

[8]  E. Eckstein,et al.  Model of platelet transport in flowing blood with drift and diffusion terms. , 1991, Biophysical journal.

[9]  P B Dobrin,et al.  Pathophysiology and pathogenesis of aortic aneurysms. Current concepts. , 1989, The Surgical clinics of North America.

[10]  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.

[11]  L V McIntire,et al.  Mathematical analysis of mural thrombogenesis. Concentration profiles of platelet-activating agents and effects of viscous shear flow. , 1989, Biophysical journal.

[12]  H. Goldsmith,et al.  Aggregation of human platelets in an annular vortex distal to a tubular expansion. , 1979, Microvascular research.

[13]  Bluth Ei,et al.  Color flow Doppler in the evaluation of aortic aneurysms. , 1990 .

[14]  S. Cooper,et al.  A canine ex vivo series shunt for evaluating thrombus deposition on polymer surfaces. , 1984, Journal of biomedical materials research.

[15]  J. Mitchell,et al.  Impact of vascular surgery on community mortality from ruptured aortic aneurysms , 1986, The British journal of surgery.

[16]  R. Budwig,et al.  Steady flow in abdominal aortic aneurysm models. , 1993, Journal of biomechanical engineering.

[17]  C. Willert,et al.  Digital particle image velocimetry , 1991 .

[18]  T. Fukushima,et al.  Visualization and finite element analysis of pulsatile flow in models of the abdominal aortic aneurysm. , 1989, Biorheology.

[19]  R M Heethaar,et al.  Blood platelets are concentrated near the wall and red blood cells, in the center in flowing blood. , 1988, Arteriosclerosis.

[20]  D. Slaaf,et al.  Localization within a thin optical section of fluorescent blood platelets flowing in a microvessel. , 1982, Microvascular research.

[21]  H. Goldsmith,et al.  Flow Patterns in Vessels of Simple and Complex Geometries a , 1987, Annals of the New York Academy of Sciences.

[22]  D. Ku,et al.  Pulsatile Flow and Atherosclerosis in the Human Carotid Bifurcation: Positive Correlation between Plaque Location and Low and Oscillating Shear Stress , 1985, Arteriosclerosis.

[23]  R C Schroter,et al.  Proposal of a shear dependent mass transfer mechanism for atherogenesis. , 1971, Clinical science.

[24]  G. Hutchins,et al.  Correlation between intimal thickness and fluid shear in human arteries. , 1981, Atherosclerosis.

[25]  H N Sabbah,et al.  Measured Turbulence and Its Effect on Thrombus Formation , 1974, Circulation research.

[26]  R T Schoephoerster,et al.  Effects of local geometry and fluid dynamics on regional platelet deposition on artificial surfaces. , 1993, Arteriosclerosis and thrombosis : a journal of vascular biology.

[27]  R. Schroter,et al.  Atheroma and arterial wall shear - Observation, correlation and proposal of a shear dependent mass transfer mechanism for atherogenesis , 1971, Proceedings of the Royal Society of London. Series B. Biological Sciences.