Atrial septal defect common or single atrium


 * Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; ; Assistant Editor-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
Common atrium is a rare variety of interatrial communication characterised by absence or virtual absence of the atrial septum.

Common or Single Atrium
Common (or single) atrium is a failure of development of the embryologic components that contribute to the atrial septal complex. It is frequently associated with heterotaxy syndrome

Anatomy
Schemating drawing showing the location of different types of ASD, the view is into an opened right atrium. HV: right ventricle; VCS: superior caval vein; VCI: inferior caval vein; 1: upper sinus venosus defect; 2: lower sinus venosus defect; 3: secundum defect; 4: defect involving coronary sinus; 5; primum defect.

Electrocardiogram
AV block has been reported in two thirds of the cases. There is an abnormal frontal plane P axis in conjunction with a frontal QRS loop consistent with persistent atrioventricular canal.

Angiocardiography
On the left ventriculogram, a typical goose-neck deformity diagnostic of persistent atrioventricular canal may be observed. Injection of contrast into the atrium demonstrates a single large globular atrial structure. This imaging study is diagnostic. It should be noted that common atrium may not be distinguished from the more frequently encountered secundum and primum types of atrial septal defects with large intra-atrial communication.