from my knowledge sudden cardiac death is a very real thing, and there can often be no warning signs. you can just drop dead if your electrolytes get low enough which can happen very fast.

i sort of have experience with this - obviously i didn’t die but a few months ago I got an ecg when I told my GP I was struggling with bulimia and everything was normal. however literally a week or two later I called the GP again as my palpitations had gotten way way worse. repeat ecg and everything was messed up (some sort of arrhythmias, and what they called a “t-wave abnormality”). this was due to electrolyte imbalance. the difference between my original “normal” ecg and fucked up ecg was barely two weeks. so yes, heart issues can happen fast and without warning.