In 1975, Alex Mitchell, 50, was watching the UK television comedy The Goodies when he burst in such hard laughter that, well, he died laughing. His heart had failed. To be fair, he didn't really die of laughter.
"Laughing can increase your intrathoracic pressure, and if you have an aortic aneurysm, that pressure can be transmitted into your vascular system, and it would rupture," Duke University School of Medicine cardiologist Jorge Antonio Gutierrez told Gizmodo in 2019. "But in that case, you just happened to laugh: the laughing didn't get you. Somebody can have a heart attack while they're laughing, but they were going to have a heart attack no matter what."
From Mental Floss:
Laughing can also prompt other bodily dysfunction, at least in theory. Vocal cords could seize up, blocking the flow of oxygen; laughing could also cause one to aspirate food into the trachea; certain connective tissue disorders, like Ehlers-Danlos syndromes, could prompt adverse reactions to spikes in blood pressure, but that's not limited to laughing. Straining or holding your breath could do it, too[…]
In 2012, the BBC reported that Mitchell may have suffered from Long QT Syndrome, an abnormality in the heart's electrical system.