I experience the same symptoms - and I haven't found a single medical professional that seems to understand that the pain we feel IS (if not the heart itself) so closely associtated with its proximity that it FEELS like the heart.
My wife is a former cardiac nurse and suggests its either angina or stomach. My response is that if it is angina...then why does it disappear almost immediately with a "burp" expelling "gas"...and it definately is NOT, repeat NOT my stomach. I DO know the difference.
So...we will have to keep trying to find a medical professional who has a better explanation than 'it's angina' or our stomach or gallbladder or any of the other explanations we are getting.
I know "gas" doesn't put pressure the heart per se...but there is SOMETHING that is associated with stomach "gas" causing the very legitimate pain in such close proximity to the heart if FEELS like the heart. Perhaps there is a neurlogical connection of a pain receptor near something that comes in contact with it because of the slight "inflation" from the "gas" - that is immediately withdrawn when the "gas" is expelled with a "burp".
I'll watch to see if anyone has a better explanation than what I and others are getting.