A welding element is provided for applying heat, chemicals, pressure, or any combination thereof to tissues inside a patient's body, e.g., a patent foramen ovale. In one aspect, the welding element is connected to a radio frequency energy source and includes an electrode and a locator. The locator facilitates positioning of the welding element and is capable of moving from an open position to a clamping position. In another aspect, a needle is provided for transseptal puncturing before the application of heat. In yet another aspect, the welding element is configured as a coil. The welding element can be made of Nitinol.