A method and devices for relieving pressure in the left atrium of a patient's heart is disclosed. The method includes using an ablative catheter in a minimally invasive procedure to prepare an opening from the coronary sinus into a left atrium of the patient's heart. Once the opening is prepared, the opening may be enlarged by a technique such as expanding a balloon within the opening. A stent is then placed within the coronary sinus of the patient, with a transverse portion expanding within the opening, allowing blood to flow from the left atrium to the coronary sinus and then to the right atrium. Pressure within the left atrium is thus relieved.