Catheter adapted for use with guide wire for accessing vessels

An ablation catheter adapted for use with a guide wire has a 3-D shaped portion that carries ring electrodes for ablating a vessel or tubular region, including the renal artery. The 3-D shaped portion, for example, a helical portion, enables the ring electrodes to contact an inner surface of the vessel at a plurality of locations at different depths along the vessel to form a conduction block without forming a closed conduction loop which would otherwise increase the risk of stenosis of the vessel. In one embodiment, the catheter has a lumen with entry and exit ports to allow the guide wire to pass through the lumen but bypass the 3-D shaped portion. In another embodiment, the catheter has outer bands providing side tunnels through which the guide wire can pass through.