Atrial septal defects (ASD) account for 10% of all congenital heart defects . Hemodynamic consequences of an ASD are dilatation of the right atrium and right ventricle (RV) because of the volume overload due to the left-to-right shunt through the ASD.For several decades, surgical closure has been considered the standard method of repairing a secundum ASD . Surgical repair, albeit enjoying a high success rate, negligible mortality, and good long-term outcome, is associated with morbidity, discomfort, and thoracotomy scars. That is why the transcatheter closure of the ASD has more recently become an alternative to the surgical procedure . During the last decade , ASD device closure , has finally replaced surgical ASD repair in most patients as the standard method of repair for the secundum ASD Cardiac arrhythmias and right chamber enlargement are well known long-term sequelae of atrial septal defect (ASD) . Therefore, many authors suggest ASD closure before adulthood . Classical ECG findings for a significant ASD are prolongation of the PR interval, prolongation of the QRS duration and right axis deviation of the QRS .

Percutaneous ASD closure is an ideal situation to study changes of RV dimensions and their impact on ECG as interferences from cardiopulmonary bypass, cardiac incisions and sutures on the right atrium and on the interatrial septum are excluded

Inclusion Criteria:

• All children under the age of 18 years diagnosed with ASD , that will undergo transcatheter secundum ASD device closure during the period of the study .

Exclusion Criteria:

• Failure to obtain informed consent .

- All children under the age of 18 years diagnosed with ASD , that will undergo transcatheter secundum ASD device closure during the period of the study .