What Arthur and Grace both appear to be describing is heartburn from reflux of stomach contents which are acid. It's well named because the symptoms can be similar to heart disease such as angina or heart attack.
The posts are not even off-topic because there is a bug involved with indigestion, called Helicobacter pylori. Over half the world's population over 40 are thought to have it, mostly without symptoms.
However, peptic ulcers and inflammation (not necessarily reflux alone) are treated by getting rid of this bug with antacids and antibiotics. It's truly a superbug, being also associated with stomach cancer and coronary artery disease.
Heartburn alone should respond to simple measures like weight loss, no smoking, raising the bed head, small regular meals, limiting alcohol, fizzy drinks, spicy foods, and taking antacids (NOT unprescribed antibiotics
)