Latent, in that he was diagnosed with it 20+ years ago and it had never been an issue until that night. There was no follow-up medical course of treatment. From the little I read up on it, in extreme cases, what I witnessed was the "reboot" of the heart's electrical system. Yes, you are correct - "perfectly fine" isn't the right description. He's vaxxed, he'll never be right again. For the time being, he seems healthy.