The present invention provides a balloon catheter comprising:a hollow inner shaft disposed within a hollow outer shaft；a balloon attached at its proximal end to said outer shaft and at its distal end to said inner shaft；wherein the inner shaft is constructed such that following radial expansion of the balloon to a first expanded state, said inner shaft is capable of responding to further longitudinal expansion of the balloon to a second expanded state by increasing its length from a resting value, and of responding to subsequent partial deflation back to said first expanded state by reducing its length back to said resting value.
