An elongate medical device shaft may comprise an elongate body and an annular electrode disposed on the elongate body. The annular electrode may define a longitudinal axis and have an outer diameter. The outer diameter may be greater at an axial center of the electrode than at an axial end of the electrode. Additionally or alternatively, the elongate body may comprise three longitudinal sections having three wall thicknesses. The middle wall thickness may be less than the proximal and distal wall thicknesses and the distal wall thickness may be less than the proximal wall thickness. Additionally or alternatively, the shaft may comprise an inner cylindrical structure and an outer tube. The outer tube may comprise a first radial layer and a second radial layer that is radially-outward of the first radial layer, the first radial layer, second radial layer, and inner structure having different stiffnesses.