pediatrics
Atrioventricular Septal Defect
Key Points
An atrioventricular (AV) septal defect may be complete, transitional, or partial; the majority of patients with the complete form have Down syndrome. A complete AV septal defect involves a large ostium primum atrial septal defect (ASD), a ventricular septal defect (VSD), and a common AV valve (often with significant regurgitation), all resulting in a large left-to-right shunt at both atrial and ventricular levels and enlargement of all 4 cardiac chambers. A partial AV septal defect also involves an ASD, but the common AV valve is partitioned into 2 separate AV orifices and there is no VSD, resulting in enlargement of the right heart chambers because of a large atrial shunt but no ventricular shunt. A transitional AV septal defect involves an ostium primum ASD, a common AV valve, and a small- or moderate-size VSD. Complete AV septal defect with a large left-to-right shunt causes signs of heart failure by age 4 to 6 weeks. Symptoms in partial AV septal defects vary with the degree of mitral regurgitation; if mild or absent, symptoms may develop during adolescence or early adulthood, but infants with moderate or severe mitral regurgitation often have manifestations of heart failure. Symptoms in transitional AV septal defect fall on a spectrum, depending on the size of the VSD. Defects are repaired surgically between age 2 to 4 months or 1 to 3 years, depending on the specific defect and severity of symptoms. 