Methods and appartus for crossing occlusions in blood vessels

A method of facilitating treatment of a blood vessel, the method comprising:

• advancing an elongate shaft of a medical device through a lumen of a blood vessel to a location proximate an occlusion in the blood vessel, the medical device including a handle assembly attached to a proximal portion of the elongate shaft;
• rotating a housing of the handle assembly in a first direction about a longitudinal axis of the elongate shaft to rotate the elongate shaft and a distal tip of the medical device in the first direction, wherein the rotating applies a torque to the elongate shaft below a first maximum torque;
• and
• advancing the distal tip of the elongate shaft between a location proximal of the occlusion and a location distal of the occlusion while rotating the housing of the handle assembly;
• wherein the handle assembly includes a torque control mechanism that transfers torque from the housing to the elongate shaft to rotate the elongate shaft in the first direction when the torque is below the first maximum torque and the torque control mechanism prevents rotation of the elongate shaft in the first direction when the torque is above the first maximum torque.