Coronary trees are pseudo-fractal objects with assymetric bifurcation self replication up to the level of myocardial penetration. Each bifurcation is an anatomo-functional entity whose 3 diameters are ruled by Murray’s law [40, 41] modified by Huo-Kassab [42] and simplified by Finet [43].

In each of the three segments of a bifurcation there is a linear relation between the diameter, the length of the distal segment, flow, and the vascularized myocardial mass. Any anatomical variation may result in a functional change.

Coronary bifurcation sites are prone to the development of atheroma [44, 45]. Proximal to the bifurcation, blood flow is laminar with a transversal diastolic flow profile and maximal velocity in the mid-segment. Flow is less rapid along the vessel walls where a high level of friction exerts a protective effect against the atheroma. In coronary bifurcations, flow is rapid and wall shear stress is high at the level of the flow divider whereas flow is turbulent, recirculating with low wall shear stess on the walls of the main vesel (proximal and distal) and the side branch opposite the flow divider. This accounts for the fact that the flow divider is initially free of atheroma.

The European Bifurcation Club (EBC) adopted a simple and open definition: a coronary bifurcation lesion is a coronary artery narrowing occurring adjacent to and/or involving the origin of a significant side branch. A significant side branch is a branch that you do not want to lose in the context of a specific patient.

Medina’s classification [46] (Fig. 16.1) proposed in 2006 and adopted by the EBC is simple and well suited to research purposes and provides a thorough description of lesion characteristics. In order to describe a bifurcation lesion accurately, it is necessary to designate the side branch (SB) from the two distal vessels. Coronary bifurcations can be described using Medina’s classification (e.g., LM, Circ, LAD where LAD is considered as the SB) [47].

A classification of the various bifurcation treatment strategies [48] (Fig. 16.2) was established by the EBC based on the positioning of the first stent (MADS). The techniques used are defined according to final stent positioning. This classification does not include balloon maneuvers such as kissing, or the Proximal Optimization Technique (POT) used to give a cross-over stent selected according to the distal diameter of the main vessel its proximal diameter corresponding to the proximal diameter of the vessel.

As described previously, coronary arteries do not have a linear reference diameter from the ostium to the distal segment but the diameter between two bifurcations is constant with a stepped reference function (Figs. 16.3 and 16.4). Conventional QCA software produce erroneous data on reference diameters (interpolated reference) especially in the vicinity of bifurcations and when the analysis is performed from the proximal segment of the vessel towards the SB [48]. There are currently at least two software programs dedicated to bifurcation lesion analysis [49, 50]. For some operators, angiographic data in bifurcations do not provide adequate information about the vessel wall and the extent of atheromatous plaque. However, although the benefit of endocoronary echography has been recently highlighted in a meta-analysis [51], potential improvements in the results of coronary bifurcation stenting under systematic IVUS guidance or CT scan have not yet been demonstrated in large randomized trials. Optical Coherence Tomography (OCT) could prove a useful tool for procedure guidance as this technique allows very rapid 3D reconstruction of the artery and the implanted stent [52].

This issue has generated a large number of publications involving bare metal stents and drug-eluting stents [53]. Of the seven randomized trials conducted with DES, six have shown that systematic double stenting does not provide any benefit [54–56].

A Chinese study (DK-Crush) on complex lesions (true bifurcation lesions with significant stenosis in both branches) showed a 1-year difference in terms of repeat revascularization in favor of the double stenting strategy following, however, systematic coronary angiography at 8 months (known to provoke a higher rate of reintervention) [57, 58].

Provisional SB stenting is currently the gold standard strategy for the treatment of bifurcation disease not involving the left main and when access to the SB is possible [59].

The results of several registries suggest that a similar approach to treatment of distal left main lesions could be considered [60, 61].

Figure 16.5 shows the different steps of this strategy. The first step consists in deploying a stent directly or following predilatation, in the main artery through the side branch into which a wire has been previously inserted. The stent size should be selected according to the distal diameter of the main branch in order to avoid carena shift towards the side branch and occlusion of the side branch. Predilatation of a diseased SB has long been the subject of debate, as it carries a risk of dissection potentially requiring a change of strategy. Following stent deployment, the proximal segment is inevitably malapposed in the proximal main vessel, which may require guide wire exchange outside the stent, and neutralize the biological effect of the DES whilst increasing the risk of thrombosis. In order to address this issue, it is necessary to implement the proximal optimization technique (POT) before any guide wire exchange. This technique consists in the complete deployment of the proximal stent segment using a balloon matching the proximal diameter of the vessel. The balloon must be short in order to prevent the occurrence of geographic miss. Any additional treatment of the SB depends on the results of subsequent angiographic examination, namely, the presence of symptoms, EKG changes, occurrence of dissection, or a suboptimal result in relation to the size of the vessel. Angiographic assessement of the result is always difficult due to the fact that the lumen of the SB ostium which is normally round, becomes oval or is reduced to a slit and is always visualized in the worst possible angiographic view. FFR [62, 63] measurement or OCT show that the SB lesion is not significant in most instances. In such cases, Kissing balloon inflation is carried out with balloon diameters matching the size of the two distal branches using a non-compliant balloon in the SB in order to avoid excessive dilatation [64]. The Kissing technique can be replaced by successive inflation of two balloons in order to avoid stent distortion due to inflation in the SB only. This strategy allows the deployment of a second stent in the SB when necessary, by using either the T stenting or the TAP technique (T and Protrusion) according to the partial protrusion of the main branch stent into the SB [65]. This can be clearly visualized using the stent enhancement technique [66].

Most bifurcation techniques can be performed through transradial approach, including techniques beginning with side branch stenting. Some techniques are more comfortable with 7 F guiding catheters which can be used transradially (specially with a sheathless) like classical crush or TAP where a balloon is present in the main branch during stenting of the side branch. Classical crush is now clearly replaced by balloon crush technique or even better DK-crush technique. The only one technique that cannot be performed in 6 F is the SKS, simultaneous kissing stent, where two stents are delivered simultaneously with creation of a neo carena. This strategy has not been compared with other strategies in a randomized trial. We will illustrate the provisional stenting strategy in non-left main and left main bifurcation lesions with single or double stenting.