This condition happens when all
the Pulmonary Veins coming back from the lungs to the Left Atrium
do not in fact empty into the Left Atrium. Instead they go through
a small chamber which then empties into a single large vein that
goes to the right side of the heart.
The fresh pink blood coming back
from the lungs mixes with the blue blood in the Superior Venacava.
This mixing of blood then goes to the Right Atrium, through a
hole to the Left Atrium, then to the Left Ventricle, and on to