Basics of Bifurcation Stenting Coronary trees are built on a fractal geometry model with a typical module, the asymmetric bifurcation, which is self-replicating over the whole coronary tree with a constant total vascular surface in the epicardial segment that maintains flow velocity and pressure. Each bifurcation has three segments: the proximal, the distal main, and the side branch (SB). These three segments have three diameters according to Murray’s law (Dprox3 = Dmain3 + Dside3), modified by Huo and Kassab (exponent = 2.3), and simplified by Finet [Dprox = (Dmain + Dside) x 0.678]. The specific anatomy of the bifurcation has functional consequences as there are linear relationships between diameter, length and flow of any vessel, and the myocardial territory supplied by the vessels. The position of the bifurcation carina or flow divider plays an important functional role.
Atheroma often develops at bifurcation sites due to specific flow characteristics inside the bifurcation. In the segments distal and proximal to the bifurcation, flow is linear with high velocity generating antiatherogenic high wall shear stress (WSS). At the level of the bifurcation, the WSS is high at the carina and low opposite the carina (turbulences). The carina is free of atheroma, at least in the initial phase of the disease, and stent struts at the level of the carina are submitted to high flow velocity, resulting in delayed endothelialization and thrombin deposit.