It turns out that her left and right ventricles are a little bit enlarged, and there is some fluid on her lungs. This is what we expected would happen, and a possible explanation for the slow weight gain recently (since she has to work harder to feed, and she's burning alot of calories). We're starting her on a diuretic tomorrow, which will hopefully make breathing a little easier for her. The cardiologist will present Demeter's case to the panel of doctors and surgeons on Friday, and we should have more of an idea of when surgery will happen then.
I also visited a friend's baby in the PICU today; she has two holes in her heart as well, and had open-heart surgery yesterday. It was very helpful to see what Demeter will be going through soon. Here is a picture of a child in PICU after surgery - Demeter will look something like this, but with more tubes!
The heart surgeons and the nurses all seemed really committed and caring - there is actually a nurse dedicated to each patient in the PICU, and, if things aren't going as planned, a doctor as well. The visit actually made me feel a little better, and a little more prepared.