An atrial septal defect (ASD) — sometimes called a hole in the heart — is a type of congenital heart defect in which there is an abnormal opening in the dividing wall between the upper filling chambers of the heart (the atria). In most cases, ASDs are diagnosed and treated successfully with few or no complications.
The most prevalent form of this defect (so-called Secundum ASD) is a defect in the central part of the "Atrial Septum" (the partition separating the Atriums). This allows red blood to pass through into the right side of the heart, leading to enlargement of the right ventricle and excessive flow in the lung circulation.
Most affected children are free of any significant symptoms, but the risk of heart failure developing later in life makes closure desirable unless the defect is minimal. These defects may be repaired surgically or by using an expanding plug ("Device"), which can be inserted through a heart catheter without an operation (Device Closure)
Other types of ASD affect different parts of the atrial septum. Defects in the lower part of the septum, close to the Atrioventricular Valves (e.g., Tricuspid valve) are called 'Primum ASD' (or Partial Atrioventricular Septal Defect).