Figure 4: Opened heart with ASD1. A - The fossa ovalis (FO) is intact as seen in the opened right atrium. The ASD1 is leftward of the fossa and immediately adjacent to the TV. A tongue of AV valve tissue (…..) covers the crest of the muscular ventricular septum. B - Septum primum (SP) is seen in the left atrium inserting (arrows) onto septum secundum (SS) and continuing to the edge of the ASD1. The superior (SL) and inferior (IL) cushion components of the anterior mitral leaflet are seen in the LV. CS - coronary sinus; LAA - left atrial appendage; RVO - right ventricular outflow; SVC - superior vena cava; ο - muscular base of the atrial septum.