A cardiac catheter for minimally invasive diagnostic and/or ablation procedures includes an elongated cylindrical, electrically non-conductive exterior tube with surface electrodes disposed on its distal portion and a handle on its proximal end. The distal portion can be curved into a curvature retained by a single action on a manual actuator. An electromechanical drive system may be incorporated into the handle. An electrical heating element may be incorporated within the distal electrode for ablation procedures. A removable, disposable blood contacting segment may be provided. The non-blood contacting actuator is thus reusable. The catheter includes two tension/compression members, which are wires with circular cross-sections that are integrally formed into ribbon-like configurations at their distal portions, for curvature formation. The handle includes a pivoted member movable in one direction by the thumb of the user's hand grasping the handle and in the opposite direction by the other fingers of the same hand.