A method of making a therapy delivery element configured for at least partial insertion in a living body is disclosed. A conductor structure is coiled around a mandrel. A segment of the conductor structure is secured to the mandrel. After this, an outer tubular structure is positioned around the conductor structure. Portions of the conductor structure that are not secured are free to expand to an inside surface of the outer tubular structure. A lumen is formed by removing at least a portion of the mandrel.