My brother has this permanently, though whether a delayed reaction to the booster or from when he got COVID itself (a relatively mild case) not long after, there's no way to know.
It has been a major detriment to his day to day life though. Any physically involved hobbies are impossible; just walking up a flight or two of stairs now leaves him completely winded for several minutes, as his heart rate also takes longer to come back to resting than before.
He's seen all the specialists. I think they ultimately came down on neurological damage, and tried a battery of drugs until they found some that slightly mitigated the problem. Last we talked about it, though, it hasn't been fully resolved.
Remember when the authorities pulled the JnJ vaccine due to adverse events after it was administered to millions of people? It seems some caution was warranted, no?
I'm being asked on a regular basis by various health practitioners (pretty much on every visit) if I ever had uneven or elevated heart rate after my covid shots (I had), then they take note which specific vaccine brand I had. So - adjust your priors ;-)
Temporarily or permanently?