A catheter for actively scoring or slicing a lesion. A catheter body includes first and second lateral openings. A selectively deployable cutter is connected to the catheter body. The cutter has a retracted configuration in which it does not perform a slicing or scoring function, such as while tracking through the vasculature, and a deployed configuration for slicing or scoring an obstruction. The cutter may include a plurality of retractable blades, such that when deployed, each blade projects in a different direction, such as from one of the lateral openings. Related methods are also disclosed.