ovale; the foramen ovale is a hole between the two atria. Once a baby is born and the lungs begin to fill with air and the blood flow of the heart changes, a tissue flap (somewhat like a trap door) called the septum primum closes the foramen ovale or hole between the two atria and becomes part of the atrial wall. The failure of the hole between the two atria to close after birth leads to a disorder called ASD primum. The most common problems with an opening found in the heart with Lutembacher's syndrome is Ostium Secundum. Ostium Secundum is a hole that is found within the flap of tissue (septum primum) that will eventually close the hole between the two atria after birth. With either type of ASD, ASD will usually cause the blood flow from the right atrium to skip going to the right ventricle and instead flow to the left atrium. If mitral stenosis (the hardening of flap of tissue known as a valve which opens and closes between the left atrium and ventricle to control blood flow) is also present, blood will flow into the right atrium through the hole between the atria wall instead of flowing into the left ventricle and systemic circulation. Eventually this leads to other problems such as the right ventricle failing and a reduced blood flow to the left ventricle. In addition to the ASD, MS can either be acquired (present either from an episode of rheumatic fever or the mother has or had rheumatic fever during the pregnancy) or congenital (the child being born with the disorder). With the combination of both ASD and MS, the heart can be under severe strain as it tries to move blood throughout the heart and lungs. Mechanism There is no exact mechanism for Lutembacher's syndrome but instead a combination of disorders as the result of Atrial septal defect (ASD) and/or Mitral valve stenosis.It is thought ASD is caused by the failure to close the hole (foramen ovale) between the right and left atrium normally found within the heart during fetal development; the creation of a hole between the atrium may also be acquired. There are two types of ASD: Ostium secundum and ASD Primum. Atrial Septal Defect Primum The failure of the hole between the right and left atrium to close shortly after birth is the cause behind ASD primum. During fetal