[Chris_RB]

Sleeping on your stomach isn't bad for your heart. However, it is the worst position you can sleep in. Sleeping prone (on your back) is the best so long as you have a decent bed, and a good pillow. Side laying is second best with the same condition as above. These positions allow your spine to be in a natural position and there is less strain on muscles. Sleeping flat on your stomach with your head to the side puts a lot of strain on your upper spine and neck muscles. There are position on your stomach which would prevent this such as having one leg bent, and laying slightly to the one side.

Everyone has different preferred positions, but to answer the OP's question, I don't see how sleeping on your stomach is bad for your heart. It's much worse for your spine. If your upper spine is out of whack, specifically your top spinal bone (Atlas), your whole body can be affected. It can cause headaches, sore neck, sore upper or lower back, and one leg can also be shorter than the other which can cause leg pain, feet pain, and lower back pain. There is a whole chiropractic technique which deals with this ideology called NUCCA. My dad is a carpenter with a bad neck and swears by it...

I think technically sleeping on your right side is easiest for your heart because of gravity. Not to say sleeping any other way is bad...your heart will function the same either way and if cardiac output is effected by how you sleep, you have bigger issues ...