Interventional systems and associated devices and methods

A system for modifying and/or removing obstructive material from a lumen of a blood vessel, the system comprising:

• a first elongated member having a proximal portion and a distal portion configured to be intravascularly positioned at a treatment site in a blood vessel adjacent obstructive material, wherein the first elongated member defines a lumen extending therethrough;
• a second elongated member having a proximal portion and a distal portion configured to be intravascularly positioned at the treatment site, wherein the second elongated member is configured to be rotatably disposed within the lumen of the first elongated member;
• a cutting element configured to cut obstructive material at the treatment site, the cutting element having a proximal end region at the distal portion of the first elongated member and a distal end region at the distal portion of the second elongated member, wherein rotation of the second elongated member relative to the first elongated member, or vice versa, causes the cutting element to expand away from a longitudinal axis of the second elongated member;
• and
• an expandable positioning element configured to be intravascularly delivered to the treatment site, wherein the positioning element is configured to be expanded into apposition with the vessel wall to position the cutting element closer to the obstructive material than before expansion of the positioning element, wherein the positioning element comprises a balloon.