We know very well why DH had his heart attack and he has been working on it for decades.
He was (he has lost a lot of weight) grossly obese and would brook no advice. He got that way over decades of hard work at it. He also has sleep apnea (which can cause heart attacks).
DD and I had been telling him for 10 years he had it but he ignored it until he had a micro sleep on the motorway, then, to be fair, he went straight to the doctor and got help. He is not alcohol dependent, and did sometimes not drink for months, but usually drank more than the recommended weekly amount.
In recent years he has taken very little exercise, mainly, because, as we know now, he had unstable angina, which meant that on some days walking to the end of the garden and back was more than he could manage, although he did manage to do an awful lot of DIY including major projects, which took much longer than planned because of the times he couldn't work because he was so breathless.
He has been a walking heart attack time bomb for years. I knew it, so did both AC, but there was nothing we could do. He is a lovely kind loving man, but he hates facing up to bad news.
If his heart attack was COVID related, he must have foreseen the pandemic back in the 1980/90s and that he would take part in a drug trial and I think thaat even you Yogagirl will find that a bit far fetched.
I am sorry but you know as little of the aeitiology of heart disease as you do of vaccines.
We only discovered yesterday that DH did get the COVID vaccine in the trial and not the alternative and very pleased we are too.