It would take some fancy shooting to hit the heart without getting at least one lung too.

I aim for the heart.

I've had heart shot deer drop in 30 yards and had one go just over 100 yards. The closer the hit is to the front/top (where the aorta and vena cava are) of the heart the faster the deer will drop.Anyhow, every deer that I've hit in the heart has left agreat blood trail (knock on wood), so that's why I prefer it.

Aim small, miss small.
(really knocking on wood now)