Hemodynamic evaluation of embolic trajectory in an arterial bifurcation: an in-vitro experimental model.
OBJECTIVE
Despite the importance of embolism as a major cause of brain infarction, little is known about the hemodynamic factors governing the path large emboli tend to follow. Our aim was to test in vitro, whether hemodynamic parameters other than flow ratios between bifurcation branches may affect the distribution of embolic particles in a Y-shaped bifurcation model, used as an analogue to an arterial bifurcation.


METHODS
In vitro experiments were conducted using suspensions of sphere-shaped particles (0.6, 1.6, and 3.2 mm) in water-glycerin mixture, using steady and pulsatile laminar flow regimes in a Y-shaped bifurcation model (identical branching angles [theta1=theta2=45 degrees] with one daughter branch diameter wider than the other [D1=6 mm, D2=4 mm]; average Reynolds number 500).


RESULTS
Experiments using naturally buoyant particles under steady flow conditions and four outlet-flow ratios revealed that small (0.6 mm) and mid-sized (1.6 mm) particles entered into either the narrower or wider bifurcation daughter branch nonpreferentially, proportionally to the flow ratios. Large particles (3.2 mm), however, preferentially entered the wider daughter branch. Moreover, as the flow ratio increases this phenomenon was augmented. Further experiments revealed that the preference of the wider daughter branch for high particle-to-branch diameter-ratios further increases under pulsatile flow and by the density ratio between particles and fluid.


CONCLUSIONS
Particles' distribution in a bifurcation is affected, beyond its outlets-flow-ratios, by the particle-to-branch diameter-ratio. The tendency of large particles to preferentially enter the wider bifurcation branch, beyond the flow ratio, is augmented under pulsatile flow conditions and is affected by particle-to-fluid density-ratio. These findings may have important implications for understanding the hemodynamic mechanisms underlying the trajectory of large emboli.
Bushi
Doron
D
Department of Biomedical-Engineering, Tel-Aviv University, Tel-Aviv, Israel. doron_bushi@walla.com
Grad
Ygael
Y
Einav
Shmuel
S
Yodfat
Ofer
O
Nishri
Boaz
B
Tanne
David
D
D000818:Animals; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D006439:Hemodynamics; D006801:Humans; D020766:Intracranial Embolism / Q000503:physiopathology*; D008955:Models, Cardiovascular; D010316:Particle Size; D011673:Pulsatile Flow; D012107:Research Design / Q000592:standards