Modern techniques of side branch protection entails positioning of a second wire into the side branch before starting the treatment of the main branch (1,16, 17). The decision to protect the side branch depends on the estimated risk of closure while treating the main branch. Unfortunately, it is impossible to predict whether or not a specific side branch will be compromised. Advancing an additional wire in the side branch is more laborious and complex than the wiring of the main branch, mandating the use of larger caliber guiding catheters, prolongs the overall procedure time, associated with larger volume of contrast media and x-ray radiation, and may be associated with increased risk of complications like coronary dissection, perforation, bleeding and contrast induced nephropathy (1). The ability to identify which side branches need to be wired and protected while working on the main vessel will make the procedure simpler and safer.