The presence of an abnormal connection between the descending aorta and the right atrium is an
accidentally discovered finding during echocardiography. The patient may be asymptomatic or suffering
from unexplained heart failure. This anomaly raises many questions about its cause. In pediatrics, this
abnormal finding should be excluded in patients who present with unusual congenital features.
Any patient showing signs of DiGeorge syndrome (22q11 deletion syndrome) should undergo a detailed
echocardiographic study, looking specifically for this anomaly, as these patients have a higher incidence
of aortic arch anomalies.
The pulmonary arch arteries (PAAs) are important in the development of the aorta and its major cervical
branches. Any abnormal connection seen in relation to the aorta is most likely due to an abnormal
genetic pathway responsible for the development of an aorto–atrial connection.
There are two forms of this anomaly: an aorto–atrial tunnel and an aorto–atrial fistula.
An aorto–atrial tunnel results from overregulation of mesenchymal cells, leading to true neovascular
formation connecting the aorta and the atrium.
An aorto–atrial fistula results from resorption of normal developing structures, associated with
downregulation of mesenchymal cell function.
The cause of both anomalies arises from changes affecting progenitor cells of the second heart field
(SHF). These progenitors are responsible for regulating the development of endothelial cells (ECs) that
line the PAAs.
