Pretty cool concept, i like the fact that you let the player litteraly draw their own path for veins.
I feel that it can be a bit tedious having to completely cut and redraw every time you have to get rif of viruses, this could be a bit more fun if you had maybe a way of battling them instead of cutting/redrawing the veins each time, and their spawnrate is a bit hectic too.
Other than that i really enjoyed it, the strategy that you can pull when connecting from the heart and having to manage having both colors connected at all times is pretty engaging and fun.
Good job :)