Internal view of the right chambers shows mild (Grade I) tethering of the tricuspid septal leaflet (asterisk). Note the nodular dysplasia of the free portion of the leaflet. Koch's triangle over the atrioventriculaar septum and the atrial septal defect are visible. The 4 chamber echocardiographic image shows grade I tethering of the septal leaflet. The atrialized portion of the right ventricle is smaller than the functional portion. The double arrow points to the atrial septal defect. K: Koch's triangle. Other abbreviations as before.