Coronary artery bifurcations (branching areas) are predisposed to atherosclerosis from turbulent flow and increased shear stress. Dilating lesions that involve a branch vessel is associated with the risk of closure of the side branch. Plaque redistribution or 'plaque shift' across the carina of the bifurcation is regarded as the responsible mechanism for the side branch stenosis and occlusion after angioplasty and stenting. Modern techniques of side branch protection require positioning of a second wire into the side branch before starting the treatment of the main branch. Placing an additional wire in the side branch is more laborious and complex than the wiring of the main branch only, is associated with additional use of contrast media and radiation, and may associated with additional risk of complications. Being able to determine which side branches require wiring for protection while treating the main vessel stenosis may make the procedure simpler and safer.