Morphology of the Lunate Fossa on the Left Atrial Surface of the Interatrial Septum and its Clinical Significance

Abstract Introduction: During the routine dissection of the hearts, in some hearts, the left surface of the interatrial septum showed the presence of strands traversing the lunate fossa extending from the semilunar fold and dividing the space of the lunate fossa. Aims: The presence of strands in the lunate fossa prompted us to undertake a detailed study of this region. This knowledge being significant in imaging of atrial septal defects (ASDs) and the transseptal catheterization procedures. Materials and Methods: Fifty adult hearts were utilized for the present study. After opening of the atrial chambers, the left surface of the interatrial septum was examined in details. The Common symbols used to mark various features on left atrial surface of interatrial septum are, Blue Star indicates- Fossa Ovalis, Red Star indicates: Lunate Fossa. Yellow Arrows indicates: Semi Lunar Fold, Black Arrows Indicates: Openings of Venae Cordis Minimi, Double Headed Red Arrow Indicates: Overlap by Septum Secundum. Results: The strands were seen in 12 hearts; the average vertical height of the lunate fossa was 7.87 mm and transverse diameter was 7.38 mm. The shape of the semilunar fold was seen to be semilunar and U, V, W, or J shaped. Probe patency of the foramen ovale was found in 16% of hearts. Conclusion: The detailed morphology of the lunate fossa and the semilunar fold assumes great significance considering the newer imaging technologies of visualization of ASDs and also the methods of transseptal catheterization in the repair of these defects.