A medical device is disclosed, including a handle assembly； an elongate body coupled to the handle assembly, the elongate body defining a guide wire lumen therethrough； and a substantially semi-circular electrode array coupled to the elongate body. The device may include a substantially rigid shaft extending distally from the elongate body and defining a lumen therethrough, the shaft including a substantially rigid segment, and a flexible coil coaxial with and extending distally from the shaft.
