This is what happened to my father: a few years later had a heart attack. As it seems (scars) he'd had several before, without knowing it.
Googled on this since I just now experienced the "heavy arms" feeling as if "muscle acked".
You have described exactly what I am experiencing. It happened the 3rd and 4th times just today, so I got on here to see what I can learn. Did you find anything out yet?