I recall a fighter from the fake old days of Bruno Sammartino, Gorilla Monsoon, and the Grand Wizard. He was named “Stan the Man Stasiak”. His specialty was the “heart punch”.
Commentators would sound like they were freaking out, saying the hapless random dude getting heart-punched was in mortal danger and the punch should be banned.
In summary, yes, I know there is some definite risk of cardiac arrest from blows to the heart. But statistically, it’s probably minuscule these days in comparison with “unexplained”.
Bob Johnson related giving a boxer such a punch in “Thunderbolt”. Similar result, except that his opponent was permanently disabled (from boxing). I guess I read that ~52 years ago...