This lesson covers fixed splitting of the second heart sound. The separation of the two components of the second heart sound remains constant during both inspiration and expiration. In this recording, the splitting is sixty milliseconds. Fixed splitting of the second heart sound (along with murmurs) indicates the presence of an atrial septal defect. This is a congenital heart defect wherein the intra-atrial septum is incompletly formed, resulting in a hole between the left and right atria. In this simulated heart sound, we have eliminated the murmurs so that you can concentrate on the fixed splitting of the second heart sound.