Various embodiments of devices and systems comprising a driveshaft for use in high-speed rotational medical procedures; e.g., atherectomy, are disclosed. Generally, the driveshaft is configured for transferring torque and activating rotation of a tool attached thereto, e.g., an abrading head, and is covered by a polymer jacket. In certain embodiments, the polymer jacket is allowed to rotate in response to the rotation of the drive shaft such that the polymer jacket is not fixed at its proximal end. Various embodiments of the drive shaft may include proximal and/or distal stops that enable the polymer jacket to move longitudinally between the stops, in embodiments comprising proximal and distal stops, or to the distal stop in embodiments comprising only a distal stop. Various embodiments of the devices and systems described herein optionally may include a metallic inner liner within the drive shaft, in addition to or instead of a polymer jacket.