People who gain high levels of command over the body can control by will the autonomic muscles so as to stop their heartbeat. This is normal in many esoteric schools.
Traditional Judeochristion thought strictly forbids it.
Uhm... I didn't create that. It was done by someone on WWP who goes by the name Incredulicide, and - I am not sure - he or she was 'inspired' by some other site.