Atrial septal defect (ASD) is one of the more commonly recognized congenital cardiac anomalies presenting in adulthood. Atrial septal defect is characterized by a defect in the interatrial septum allowing pulmonary venous return from the left atrium to pass directly to the right atrium. Depending on the size of the defect, size of the shunt, and associated anomalies, this can result in a spectrum of disease from no significant cardiac sequelae to right-sided volume overload, pulmonary arterial hypertension, and even atrial arrhythmias.
With the routine use of echocardiography, the incidence of atrial septal defect is increased compared to earlier incidence studies using catheterization, surgery, or autopsy for diagnosis. The subtle physical examination findings and often minimal symptoms during the first 2-3 decades contribute to a delay in diagnosis until adulthood, the majority (more than 70%) of which is detected by the fifth decade. However, earlier intervention of most types of atrial septal defect is recommended.
The 3 major types of atrial septal defect (ASD) account for 10% of all congenital heart disease and as much as 20-40% of congenital heart disease presenting in adulthood. The most common types of ASD include the following:
Ostium secundum: The most common type of ASD accounting for 75% of all ASD cases, representing approximately 7% of all congenital cardiac defects and 30-40% of all congenital heart disease in patients older than 40 years.
Ostium primum: The second most common type of ASD accounts for 15-20% of all ASDs. Primum ASD is a form of atrioventricular septal defect and is commonly associated with mitral valve abnormalities.
Sinus venosus: The least common of the three, sinus venosus (SV) ASD is seen in 5-10% of all ASDs. The defect is located along the superior aspect of the atrial septum. Anomalous connection of the right-sided pulmonary veins is common and should be expected. Alternate imaging is generally required.
Sex: ASD occurs with a female-to-male ratio of approximately 2:1.
Age: Patients with ASD can be asymptomatic through infancy and childhood, though the timing of clinical presentation depends on the degree of left-to-right shunt. Symptoms become more common with advancing age. By the age of 40 years, 90% of untreated patients have symptoms of exertional dyspnea, fatigue, palpitation, sustained arrhythmia, or even evidence of heart failure.