Medical device with means to improve transmission of torque along a rotational drive shaft

A catheter device for insertion into bodily lumens or cavities, comprising:

• a) an elongate hollow sheath having a longitudinal axis having distal and proximal end portions and an elongate midsection;
• b) a functional therapeutic or diagnostic medical device mounted in the distal end portion of said elongate hollow sheath;
• c) a rotational drive mechanism extending through said elongate hollow sheath from said proximal end portion to said distal end portion, said functional therapeutic or diagnostic medical device being connected to said rotational drive mechanism such that said rotational drive mechanism imparts rotational motion to said therapeutic or diagnostic medical device about said longitudinal axis within, and with respect to, said elongate hollow sheath;
• and
• d) one or more frictional components mounted in said elongate hollow sheath located generally in said distal end portion and bearing radially outwards to be in frictional contact with an inner surface of said elongate hollow sheath so that during rotation of said functional therapeutic or diagnostic medical device by said rotational drive mechanism the rotational drive mechanism operates with a higher torsional load than in an absence of said one or more frictional components thereby reducing non-uniform rotational distortion as said functional therapeutic or diagnostic medical device rotates inside said elongate hollow sheath.