A device for treating a lesion in a body lumen to enlarge a passageway in a body lumen comprising a cutting member (20, 120, 120', 130, 130') having a proximal portion and a distal portion (23, 222, 132) and a tracking member (30, 140) having a proximal portion and a distal portion (142). The cutting member and tracking member are connected at their distal portions and insertable into the body lumen as a unit, the cutting member configured for movement in a direction transverse to a longitudinal axis of the tracking member to widen a gap between the cutting member and tracking member at least at a distal region.
