Boundary layer separation in a plexiglass model carotid bifurcation was investigated in relation to the origin of atherosclerotic plaque clinically found in this region. Our model was comparable to a human carotid in both dimensions and geometry. T he predilection for atherosclerosis to occur at bifurcations in the arterial tree is well documented. 1 ' 2 This finding led to the hypothesis that hemodynamic factors are in some way involved in atherogenesis, although the precise nature of the flow or pressure changes favoring atherogenesis is not yet well understood. In humans, one of the most common sites for localization of atherosclerosis is at the carotid bifurcation, especially at the origin of the internal carotid artery where it may be the cause of transient ischemic attacks or stroke. model of the human carotid bifurcation based on averaged data from angiographic measurements. The flow field within this bifurcation model was studied with the laser Doppler anemometer under steady flow conditions, and velocity profiles across the bifurcation determined. 8 This work demonstrated a large region of flow separation and low wall shear stress at the origin of the internal carotid. In previous work from this laboratory, we have demonstrated the three-dimensional nature of separation and secondary flow in model anastomoses and bifurcations.
910The Balasubramanian model does not incorporate the curvature of vessels that is seen on arteriography. We have taken the internal measurements from Balasubramanian's model and have superimposed on that the curvature of vessels seen in the arteriogram of a carotid artery with atherosclerotic plaque present at the bifurcation (figure 1). This model is, therefore, a very close approximation of the carotid bifurcation seen in figure 1 prior to the formation of the atherosclerotic plaque. This allows us to demonstrate the flow field under steady and pulsatile flow conditions. The relevance of these studies to the formation of atherosclerotic plaque is also discussed.