A catheter includes a handle, a catheter sheath and a stylet having a shaped distal part received within the catheter sheath. The catheter further has a shape adjustment mechanism including a stylet carrier displaceably carried by the handle and a shape adjuster in the form of a collar rotatable about the handle. Rotational movement of the shape adjuster imparts a motion to the stylet carrier to adjust the shape of the distal part of the stylet.