An ablation apparatus may generally comprise an elongated body having a proximal end and a distal end and a non-conductive tip at the distal end, a conductive sheath at least partially surrounding a portion of the elongated body intermediate the proximal end and the tip, and an electrical conductor electrically connected to the conductive sheath. The ablation apparatus may comprise a first electrode having a first diameter and a plurality of second electrodes each having a second diameter, wherein the first diameter is greater than the second diameter. Methods of using the ablation apparatus are also described.