I was ill at Christmas, while it may not have been CV it followed the pattern of the illness including the time it's taken me to recover.
It may even have been me my post you read. I am a marathon runner, not fast, but like to think I was extremely fit and regularly ran 13 miles plus for fun.
I first got ill on 23rd of December, whatever I had knocked me for 6, put me in bed barely able to move for 3-4 days and then tired me really quickly.
I first attempted to run on 1st December, slower than slow (think I could have walked quicker), tired really quickly, having to take inhaler couple times (before this illness I hadn't used an inhaler in over 3 years). My heart rate going through the roof.
Tried again a week later, used inhaler before I started, still ridiculously slow and unable to keep going for even a fraction of the time.
Few days later I re-started training with my trainer, she was concerned about my heart rate and wouldn't allow me to do half of what I usually would (and I couldn't have anyway, I tired so quickly and heart rate was going up so high), I didn't even need to rest in Zumba 2 days after running a marathon but was taking several breaks in the class for weeks.
Over 3 months it gradually improved, I still had an alarm to alert us if my heart rate went too high and couldn't push as hard as usual and was still using inhaler. But reckon I was 90% fit by the time the lockdown started.
Now, 4 months later I'm gradually building my distance back up. Would say I'm 99% where I was before I got ill.
Again I don't know what I had and if it wasn't CV then it just shows that other things are just as nasty.