The present invention provides systems and methods for occluding or closing a patent foramen ovale of a patient (PFO). The invention includes a catheter carrying an energy delivery element. The catheter introduces the energy delivery element into the patent foramen ovale of a patient's heart. Once appropriately positioned, the energy delivery element applies energy, such as radiofrequency energy, to the tissues surrounding the patent foramen ovale. The application of energy causes the tissues to join together, occluding the patent foramen ovale. The energy delivery element may be removable or permanently implanted in the patent foramen ovale.