A congenital malformation, in which the partition wall between the heart chambers is not perfect and blood passage through the septum is possible.
The defect can be located in the septum separating the upper compartments of the heart (atrial septal defect, ASD) or in the septum dividing the ventricles (ventricular septal defect, VSD).
The presence of such defect results in leakage of blood, predominantly from the left side, where pressure is higher, to the right. The right side will have to cope with greater load and this can result in Pulmonary Hypertension with subsequent cardiac insufficiency. If necessary, such defects can be surgically repaired.