There are two atrium and two ventricles in heart. Atrial septal defect is a congenital defect, a hole in the atrial septum which is a layer between left atrium and right atrium.

Types of ASD,
a) Secundum ASD (80% of ASDs; located in the region of the fossa ovalis and its surrounding)
b) Primum ASD [15%, synonyms: partial atrioventricular septal defect (AVSD), partial atrioventricular (AV) canal; located near the crux, AV valves are typically malformed resulting in various degrees of regurgitation]
c) Superior sinus venosus defect [5%, located near the superior vena cava (SVC) entry, associated with partial or complete connection of right pulmonary veins to SVC/right atrium (RA)]
d) Inferior sinus venosus defect [,1%, located near the inferior vena cava (IVC) entry]
e) Unroofed coronary sinus [,1%, separation from the left atrium (LA) can be partially or completely missing].

The left atrium is the structure which drains oxygenated blood from lungs. Right atrium is the other atrial structure of heart which takes deoxygenated blood from the body. If there is a hole between these two structures, a part of the oxygenated blood mix between the deoxygenated blood. The amount of this mixture is directly related with the size of the hole. If there is a large ASD, the shunt between these two structures will be high and regurgitant blood from left to right atrium will be pumped against to the pulmonary system. This will cause much work on lungs.
If it is not diagnosed, right ventricular and right atrial enlargement, severe right heart failure, pulmonary hypertension, reverse shunt due to the pulmonary hypertension, paradoxal embolism, severe arrhytmias and death can develop.
The most common type of the ASDs is ostium secundum type ASD. In past, the only treatment of ASD was closure with a patch by open surgery. However, we can close ostium secundum type of ASDs with percutaneous transcatheter method both in children and adults. For the other types of ASD, we still offer surgery.

Echocardiography is an important diagnostic tool for the diagnosis of these defects. Transthorasic echocardiography make a probable diagnosis but a definite diagnosis is made by transesophageal echocardiography. After detection of colour Doppler jets across the atrial septum by using 2D-TEE, real time 3D-TEE usually confirms the definite diagnosis. Three D TEE can also better show us the location and number of the defects and can confirm us whether the defect can be closed without surgery or not. We are using 3D-TEE in our clinic in all patients with the suspicion of atrial septal defect.

How do we apply percutaneous transcatheter atrial septal defect closure?