The present disclosure relates to devices and methods for implanting a prosthesis into a heart of a mammal, such as a person. The disclosure includes a prosthesis that acts as a pressure vent between the left and right atria of the heart. The disclosure also includes a mounting tool for mounting the prosthesis onto a loading tool, the loading tool useful for loading the prosthesis onto a device for delivering the prosthesis into the patient's heart. Control devices and methods for using these devices are also disclosed. The intracardiac pressure vents disclosed allow sufficient flow from the left atrium to the right atrium to relieve elevated left atrial pressure and resulting patient symptoms. The devices also limit the amount of flow from the right atrium to the left atrium to minimize the potential for thrombi or other embolic material from entering arterial circulation.
