IntroductionCoronary artery bifurcation lesions comprise one of the more complex lesion subsetsroutinely faced in interventional cardiology, accounting for up to 20% of all coronarydiseases treated by percutaneous coronary intervention (PCI) The technical difficulties inherent in the treatment of bifurcation lesions, associatedwith their lower success and higher complication rates compared with non-bifurcationlesions, have always been the object of intense research activity, with publication ofcontemporary studies in the past few years contributing significantly to the decisionmaking process.Bifurcation lesions are challenging to categorize, since they are variable not only intheir anatomy (location of plaque, plaque burden, angle between branches, site ofbifurcation, and size of branches), but also in the dynamic anatomic changes duringtreatment caused by dissections and carina shift. Despite these challenges complicatingclassification of bifurcation lesions, many definitions have been proposed in an effort tounify this common clinical situation. A coronary bifurcation lesion is defined as (coronary artery narrowing occurringadjacent to, and/or involving, the origin of a significant side branch). A significant sidebranch (SB) is a branch that, if lost, can impact the prognosis of the patient. General different classifications of coronary bifurcation lesions have been proposed, dueto the variety of possible bifurcation lesions, with different technical implications,treatment options, and prognosis. The most used, for its simplicity and reproducibility,is the Medina classification. This classification is based on the presence or absence ofnarrowing >50% on each of the three components of the bifurcation: the main branchproximal (MBP), the main branch distal, and the SB. A value of 0 or 1 is assigned toeach of the three segments in the following order: MBP, main branch distal, and SB. Forexample, a bifurcation lesion involving the MBP and the SB would be defined as 1, 0,1. Seven morphologies are therefore possible. Despite being the most usedclassification, the Medina has several limitations, since it does not consider the plaqueburden, branch diameter, lesion length, bifurcation angles, the presence of ostialdisease, or calcification.