But unexpected cardiac arrest happened long before the Covid vaccine...

One of my family friends growing up was a doctor in his mid 40s. He was in great shape and ran every other morning. Drank green smoothies and the whole 9 yards. Dude just dropped dead on a run one morning. Two autopsies found absolutely nothing - no clogged arteries, no heart malformation, no known toxins. Just sudden cardiac failure. This was like 2003 ish, long before anyone but specific disciplines of scientists knew the word coronavirus.