@musicfreak12
Nah, that was invented in the 1800s by people who assumed nobody before them could have been intelligent, and when the original reason was less widely known they used the heart-stopping thing as a reason for always saying it.
It's actually a really fascinating study of a social meme that's lasted for over 600 years; people start saying "may god bless you" because death was likely imminent, and then they keep saying it. When some kid asks his mom "why why why?!" she makes up a story about your heart stopping (it doesn't stop, BTW) and it gets repeated amoung the common people until everybody says it... and 600 years after it starts, we still say "bless you" after a sneeze.
It's like "Merci" in French; it was "Grammercy" in the middle ages, and "Gran Merci" in the Roman Empire over 2000 years ago... and they still say it.