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Figure 2 Gross anatomy of the patent foramen ovale. (a) View from the right atrium showing a patent foramen ovale. Patency is determined by probing. The limbus (arrow) is seen forming a rounded cuff around the valve of the foramen ovale. The anatomic locations relative to the coronary sinus (CS) and tricuspid valve (S = septal leaflet; A = anterior leaflet) can be appreciated. (b) Same case viewed from the left atrium with probe demonstrating patency. The anterior leaflet of the mitral valve is seen below the probe.