Radio frequency ablation system

The present invention relates to medical devices in general, and in particular to radio frequency atherectomy devices for removing intravascular occlusions. An RF ablation system includes a catheter and an RF electrode that delivers RF electrical energy to the site of an occlusion. The system includes a mechanism for minimizing the likelihood that RF electrical energy will be applied directly to the vessel wall. In one embodiment of the invention, the catheter includes a number of tissue expanding jaws to engage a vessel wall and push the vessel wall away from the electrode to shield vessel walls from the electrode. In yet another embodiment of the invention, the electrode has a spiraled distal end with a radius that is larger than the radius of the catheter, such that the electrode engages the vessel wall and pushes the wall away from a conducting portion of the electrode. The portion of the electrode that engages the vessel wall is preferably coated with an insulating material to prevent delivery of RF electrical energy directly to the vessel wall.