Elongate medical device including chamfered ring electrode and variable shaft

An elongate medical device assembly comprising:

• an elongate shaft body comprising:
• an inner cylindrical structure defining a longitudinal lumen and defining a longitudinal axis;
• and
• an outer tube, disposed radially-outward of the inner cylindrical structure, comprising a first radial layer and a second radial layer that is radially-outward of the first radial layer, the first radial layer having a different stiffness than the second radial layer;
• wherein the inner cylindrical structure and the outer tube comprise an intermediate axial portion of the elongate shaft body, wherein the elongate shaft body further comprises:
• a distal end portion, axially-distal of the intermediate axial portion;
• and
• an annular electrode configured to deliver ablative energy and disposed on the distal end portion, the annular electrode having an outer diameter, wherein the outer diameter is greater at an axial center of the annular electrode than at an axial end of the annular electrode;
• and
• wherein the elongate shaft body has an outer diameter, wherein the outer diameter of the axial end of the annular electrode is radially within the outer diameter of the elongate body and wherein at least a portion of the outer diameter of the elongate shaft enlarges around a portion of the annular electrode.