I have a dd with TS who is now nearly 5. I'm presuming that an ultrasound scan picked up some tubers in the heart? I can't imagine how you're feeling right now , probably shocked, and you must have so many questions in your mind.
One of the things about TS is that it is very unpredictable at the early stages and it's really unclear how things will develop and in some ways that's one of the hardest things.. the uncertainty..
But I would suggest that you make contact with the TS Association in the UK as they have fantastic advisors/nurse specialists who will be really happy to talk through all your concerns that you've got right now.
Pinkorkid is right, that there is such a wide variation in severity and some people have the TS gene but no symptoms and others have very severe presentation.
Our dd has widespread multiple tubers in the brain and of course there are lots of implications from these.. DD also had heart tubers early on but these resolved as they usually do in the heart..
The important thing is to take on day at a time, and look after yourself..
Please feel free to ask away or to PM me if you'd like.. There are a couple of mothers who have kids with TS on this forum but there are not many of us around.. The TS forum in the UK is very slow and quiet but the US one is busier. It's early days yet though. Try if you can not to overload yourself with information.. I did that and quite quickly wished I hadn't.. it's hard not to go looking for info as a way of trying to understand what's happened..and to try to prepare for what's to come too..
I'm sure you'll get a lot of support from this forum over the months ahead..
Do take care..