The Left Main or “Widow Maker” is the largest bifurcation of the coronary tree and has a number of unique features, which may demand different technical approaches from non-left main bifurcations. The proximal reference diameter generally measures between 4.5 and 5.5 mm - close to, or above, the dilatation limit of most currently available coronary stents.

The side branch is most often the circumflex artery (Cx) or (LCx) which generally has a large diameter. It is not always easy to access and one of the reasons is that its bifurcation angle is generally T-shaped (closer to 90º). This may impact on technique and the prognosis after stenting.

The myocardium supplied by the LM generally accounts for considerably more than 50% of the total myocardial mass so occlusion of the Cx is not acceptable since it often results in ischaemia of a large myocardial territory and may induce acute ischaemic mitral regurgitation.