Since a scene in Ancient Scars deals with how much blood a heart can produce with each beat, I had to search that out. Turns out the answer is that it can produce up to 5 liters of blood per beat. Quite a bunch there.

Here are some other interesting facts about the human heart –

http://facts.randomhistory.com/human-heart-facts.html

And here is another – http://hypertextbook.com/facts/2003/IradaMuslumova.shtml