Blue blood = blood that has NOT recieved oxygen yet

Red blood = blood that HAS been oxygenated

Purple blood = "red" and "blue" blood that have mixed together.

A little decoding help if you want it: RA = Right Atrium (where the "blue" blood returns from the body) RV = Right Ventricle (receives "blue" blood and sends it out to the pulmonary artery for oxygen, to make it "red".   PA = Pulmonary Artery (sends "blue" blood to the lungs for oxygen) LA = Left Atrium ("red" blood goes there from the lungs after getting oxygen) LV = Left Ventricle (largest and strongest part of the heart. Pushes "red" blood with oxygen to the rest of the body.  Part that Natalie was missing.) AO = Aorta (the major vein that pumps blood with oxygen, "red" blood, to the whole body. VERY narrowed in this defect.) PDA = Patent Ductus Arteriosis (part of normal fetal circulation, but closes in the first 24 hours when no longer needed, when they can breath oxygen on their own.  This is what kept Natalie and other babies alive and caused so much trouble when it started to close.  The medicine they gave her, Prostaglandin, kept this duct from closing, and kept her with us until surgery.  It may only be given for around a week.)