US Patent 7413558 Elastically distensible folding member

An elastically distensible folding member is disclosed. The folding member can be formed with a wall that is substantially shaped as a tube when the folding member is in a relaxed (i.e. unstressed) state. The tubular shaped folding member defines a tube axis and can have an axially aligned slit that extends through the wall. The folding member can be used to cover an incising element that is attached to the balloon and positioned in the lumen of the tubular folding member. During balloon inflation, the folding member can be deformed to expose the tip of the incising element to allow for a tissue incision.