Click on image to view larger version.

Figure 1 (A) Transthoracic echocardiographic image of type A atrial morphology. The distinction between septum primum (prim) and septum secundum (sec) can be seen. Arrows denote the decompression pathway from the left atrium (LA) to the innominate vein, right superior vena cava and right atrium (RA). This pathway is unobstructed. (B) Doppler flow in the ascending limb of the decompression shows low velocity, phasic flow confirming the absence of significant obstruction.