Can't be too sure...
No one symptom definitively indicates a heart attack
is or is not in progress (many people make the fatal mistake of waiting out atypical heart pain).
In fact, "heart pain" is often indistinguishable from esophageal, pericardial, mediastinal, gastric, and chest wall distress. By the same token, where in your gut you retain "trapped gas" may give you very different sensations. See doctor to be sure.