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Background
Atrial septal defects (ASD) are among the most common congenital heart lesions. They can occur in isolation or as part of more complex congenital heart defects. This section covers isolated ASD. Atrial septal defects can be classified into 4 types: 1. Secundum type ASD, 2. Sinus venosus defects, 3. Primum ASD (as part of the spectrum of atrioventricular canal defects), and 4. Unroofed coronary sinus ASD. The most common type is the secundum type ASD and this type of ASD is the focus of this section.
Depending on their size, ASD can lead to volume overload of right-sided heart chambers with dilatation of the right ventricle and right atrium. Large ASD are often detected in early childhood and patients undergo surgical or interventional closure. Not uncommonly however, ASD can remain unrecognized until adulthood. ASD may be diagnosed incidentally or may be diagnosed when patients present with complications. Late complications of ASD are right heart failure, atrial arrhythmias (mainly atrial flutter and atrial fibrillation), and paradoxical embolism. Rarely there is an association with pulmonary hypertension and the development of Eisenmenger syndrome (see Eisenmenger Syndrome). The diagnosis of an ASD is sometimes made during pregnancy when an echocardiogram is done to investigate a flow murmur.
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