Betul Yilmaz Furtun, MD
An atrioventricular septal defect (AVSD) describes a constellation of defects defined by deficient atrioventricular septation and a common atrioventricular junction. The variability seen in atrioventricular septal defects is then determined by both the position of the common atrioventricular valve within the atrioventricular septal defect as well as the presence or absence of bridging tissue between the superior and inferior bridging leaflets.
AVSD Subtypes
Secondary to deficiencies in both the atrial (primum ASD) and ventricular (inlet VSD) septae, the distance from the crux of the heart to the apex is foreshortened and the distance from the apex to the aorta is increased and results in an elongated LVOT (“goose neck” deformity) with anterior displacement of the aorta.
AVSD accounts for approximately 4% to 5% of infants with CHD and occurs in 0.19 to 0.35 per 1000 live births.
AVSD may be associated with conotruncal anomalies such as tetralogy of Fallot (TOF) and double outlet right ventricle (DORV). AVSD can also occur in heterotaxy syndrome and is more common in asplenia (bilateral right atrial isomerism) than in polysplenia (bilateral left atrial isomerism).
Depending on the morphology of the superior leaflet of the common atrioventricular valve, three types of AVSD have been delineated (type A, B and C, according to Rastelli's classification). The anatomic subgroups (Rastelli's type A, B and C) can be classified on the basis of the chordal insertions and morphology of the superior bridging leaflet of the common atrioventricular valve.
Rastelli Types
An AVSD is classified as balanced or unbalanced. In balanced AVSD the common AV valve is equally distributed to the right and left ventricle. An unbalanced AVSD accounts for 10% of all AVSDs and occurs when the AV valve is mostly or primarily committed to one ventricle. Approximately two thirds of unbalanced AVSDs are RV dominant. RV-dominant AVSD is frequently seen with hypoplastic LV, aortic valve hypoplasia, LVOT obstruction and aortic arch anomalies such as coarctation of the aorta. Similarly, in LV-dominant AVSD, the RV is hypoplastic, and there are associated RVOT obstruction and pulmonary stenosis or atresia.
Genetic Considerations
Fetal Imaging Pearls:
Fetal Surveillance:
Prostaglandins (PGE)