[quote=Shikaru]
Magnus as well as Dresden had their hearts artificially removed, don't ask me how exactly but yea. Due to this they have far less restrictions for a normal vampire. Expect a post from me shortly or tommorrow if I fall asleep mid-post :p
[/quote]

Well, it's possible that a vampire has muscles along their blood vessels, which makes having a heart redundant. They certainly don't seem to need any other vital organs, so most likely the heart thing is a magical effect.