The three circled areas represent 1.) Pulmonary stenosis/atresia in the pulmonary arteries [the 'T' shaped thingy] 2.)MAPCAs [the twig-like thingys growing off of the aorta] and 3.) the VSD [hole between left & right ventricles (blue and red parts)] (stenosis=thinning/atresia=absent)(aorta=the fat pink vessel connected to the red side of the heart in this pic... the aorta is the largest artery in the body, originating from the left ventricle of the heart and bringing oxygenated blood to all parts of the body)
As mentioned previously, if the "T' shaped thingy represents a tree [a trunk and two branches]the vertical part of the "T" [the trunk], is missing in Scarlett and the horizontal parts of the "T" [the branches] are very small just like this picture.
During Scarlett's surgery, Dr. Cleveland is going to implant a homograft/conduit (from a human cadaver) to replace the 'trunk' in the aforementioned analogy. He is then going to test the pressures in the 'branches'. Depending on the pressures, he can do one of two things. 1.) He can cut off some of the collateral arteries (MAPCAs) [aka the 'twig thingys'] and dispose of them...or 2.) He can cut off the MAPCAs, bind them together and create a make-shift 'branch' to help the undersized existing branches.
While up during one of my midnight-2am-4am feedings, I found a pretty complex report/presentation on Pulmonary Atresia VSD. I don't know when it was dated, but I did see 2003 somewhere so it was at least a few years ago. If you have extra time on your hands and you're really bored and have nothing better to do (like at 3am when you're up pumping like me ;)..., it's interesting reading. It's 56 pages long....but here it is: Management and classification of collateral vessels in Fallots with Pulmonary Atresia and VSD. Warning tho, there are a few graphic pictures so it's not for the weak-stomached.
Back to her surgery... if the pressures in her branches are too high, then Dr. Cleveland will just backpeddle and implant a bigger shunt. Like pictured below. This is basically what her heart looks like now (minus the 'trunk') you can see the BT shunt at the top of the pic connecting the aorta (big fat light pink vessel) to the underdeveloped pulmonary artery branches: