A medical instrument tip for penetrating tissue may include a body having a diameter of less than 5 mm, and a blade having a plurality of faces and a plurality of cutting edges. At least one cutting edge may have a dihedral angle of less than 50 degrees. A medical instrument tip may be included in an ablation instrument that also includes a cable and a conductive antenna body coupled to the cable for delivering ablative energy to a target tissue. A medical instrument tip may be configured to pass through a working lumen of a catheter having an inner diameter of less than 5 mm such that the medical instrument tip may penetrate a target tissue
