I usually don't reply to this type of posts, because I feel that it would be very wrong to speculate in what could have caused such a tragic happening. I can't do anything but say I'm very sorry to hear about your loss.
If I should add anything, I doubt that varicose veins had anything to do with this. Neither can I or will I speculate if any of the psychiatric diagnoses had anything to do with this. Since you are posting in the arrhythmia forum, I would assume you suspect that he suffered some sort of acute arrhythmia causing cardiac arrest. Unfortunately this can happen even to healthy individuals, but it's very very rare.
Again, my most sincere sympathy. And sorry I am not able to provide a better answer.
I can't help with the diagnosis, but I do sympathize. The young age of 52 adds to the sadness.
Being the one to discover the dead person just adds to the pain. While it was not my brother, I discovered a neighbor who had died in his front yard from a heart attack. I believe that added to my sadness from loosing a good friend.
This forum may have some experience that directly relates. I don't know that the vicarious veins is related, but I doubt it.
My sympathy.