Excedrin has aspirin, acetaminophen (the active ingredient in Tylenol) and caffeine in it.
You could be having a reaction to any one of those. Aspirin can cause digestive problems, including heartburn... and worse, in large doses, or taken frequently, intestinal bleeding.
Sensations of heartburn aren't always felt in the chest and maybe you are simply sensitive to aspirin and are experiencing atypical heartburn.
Maybe it's even the caffeine?? Just a wild guess.
Years ago I remember I could not take Excedrin because it gave me almost instant heartburn. Not today though. Odd huh?
Your symptom doesn't sound ominous.
As an experiment, with your next headache could you avoid Excedrin?
Just brainstorming here- but it would be interesting if you got this sensation with just aspirin alone or tylenol alone.
zuzu xx