NATO - first, congrats on the deer. But I'm a bit confused on the shot. You said the deer was quartering hard toward you and you shot behind the shoulder and exited out the abdomen. But you hit the heart? Unless that deer was arranged incorrectly there would be no way you could have hit the heart with that shot. In order to hit the heart qtring toward you depending on how hard, you would have had to either go thru the shoulder or the front point of it and also a few inches lower. I would guess the bullet passed thru the near side lung, then the liver and exited out the other side. Now at that range there may have been sufficient hydro shock (hydra shock) to rupture the heart. But I don't think the bullet could have hit it.
Now don't get me wrong, I am not critiquing you. Just trying to help. Remember you don't always shoot behind the shoulder.
The method I use when shooting at a deer for the location of the vitals is to picture a soccer/volley ball between the shoulders up against the brisket. Aim for the center of the ball and 9 out of 10 you will anchor that deer right were it stands. Now that being said, you need a quality bullet to get thru the shoulder. Anything less you better wait for a broadside or quartering away shot for success.
Again, Congrats on your deer.