Investigation of Hemodynamics In Saccular Aneurysms
Marjan Rafat1, Martin Heller2, Howard A. Stone1, and Debra T. Auguste1. (1) School of Engineering and Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138, (2) Micro- and Nanotechnology, Technical University of Denmark, Building 345 East, DK-2800, Kongens Lyngby, Denmark
The mechanisms behind aneurysm growth and rupture are unknown. An increased understanding of hemodynamics, mechanical forces, and biological response within an aneurysm may enable aneurysm prediction, improve diagnosis, and allow development of new treatment strategies. We analyzed flow patterns in clinically relevant aneurysm geometries using the finite-element method to solve the incompressible Navier-Stokes equations numerically. Our analysis consists of a two-dimensional, steady-state flow over a range of Reynolds numbers (0 < Re < 500), which accounts for patient variation in blood pressure (velocity) and hematocrit (viscosity). The aneurysm geometry was varied systematically using height to width ratios. In addition, we studied aneurysms placed at the midpoint of a bifurcation, offset from the midpoint of a bifurcation, and on a lateral vessel. We observe the formation of symmetric and asymmetric flow profiles, with the appearance of closed and open eddies. The distinguishing features of the different flows are mapped as a function of Reynolds number and geometry. This work evaluates flow patterns for different aneurysm geometries, which may dictate effects caused by mass transfer and mechanical stress on the biological response. Small changes in the geometry or Re could result in distinct changes in the hemodynamic profile, which may (1) correlate with an increased incidence of rupture or (2) be used to manipulate the biological response to impede rupture or growth. Our nondimensional analysis may be broadly applied to a wide range of aneurysms and patient specific cases.