Embodiments of the present invention are directed to ablation catheter systems configured, for example, to ablate tissue adjacent an ostium of the pulmonary vein in a left atria of a heart. In one embodiment, an ablation catheter system includes a handle including an actuator and a catheter coupled to the handle defining a lumen extending through a length of the catheter, the catheter including a tip portion at a distal end thereof. The ablation catheter system may also include an electrode coupled to the handle with lines extending through the lumen of the catheter, the electrode being configured to be constrained within the tip portion of the catheter and configured to be deployed from the tip portion and self expand to an expanded configuration. With this arrangement, the electrode is configured to self expand to a conical configuration with a tip portion configured to be disposed within the pulmonary vein.