Greetings Dr.Sing and welcome to EVC. I'm disappointed to join the thread this early as I am definitely not as knowledgeable as most of the regulars that will hopefully join in this discussion soon, but I can give generalised answers to your questions. That will have to suffice for now, but I think your post is extremely well formulated and deserving of serious replies.
I'll make my reply brief, as I can't speak to the specifics of this in the way that others will undoubtedly do in due course.
You said:
But someone was smart enough to program the heart not to do this.
I was relishing every word up to this point, but this was a dramatic leap. It is at this point that you are essentially restating Paley's argument (or argument from design), that design implies a designer.
Darwin's greatest contribution to science is that he completed the Copernican Revolution by drawing out for biology the notion of nature as a system of matter in motion governed by natural laws. - Francisco J. AyalaSource:
Just a moment...
To feebly attempt to answer your two succint questions I would say as follows, but I eagerly anticipate the replies of others with more specific knowledge:
1. How do you explain such an intricate complex programming system?
As the result (and not the end result) of an unimaginably long period of gradual changes throughout the history of life on Earth during which time primitive hearts either failed (thus vanishing from the evolutionary line, or at least stagnating at a lower level of complexity) or succeeded (leading to the successful reproduction in offspring) and eventually leading to what might be interpreted as "intelligently designed". "Purposefully evolved" makes more sense to me, that purpose being to survive.
2. If you do not consider this mechanism to be'programmed by someone', why not?
Quite simply because there is an alternate explanation (the ToE) that elegantly eliminates the need for supernatural intervention.
Sorry that I'm not really getting to the "meat" of your question. I hope others will do so. Thanks again for a concise and well-worded post.
Edited by Briterican, : Preview fail.