In "The Tell-Tale Heart," what does the heart beating symbolize?

To me, the beating heart in "The Tell-Tale Heart" symbolizes the murderer's conscience and/or his guilt.  It seems as though this man  knows that he has committed a horrible crime and the guilt is literally destroying him, eating him up inside like a living creature fighting its way out.  Though a manifestation of his mind,the beating heart is real enough to him to drive him to the verge of insanity and to an admission to the crime.