Originally Posted by Carbonfiberboy

It's too bad that the usual suspects who know absolutely nothing about the subject jump in and argue nonsense. If you don't know anything about it, just don't post. Now that's an idea.

I happen to know all about this because I've been tracking my HR in hard training for over 20 years, every single workout I've done, plus morning resting and morning standing HRs, plus now HRV. Why? Because more information is better than less information and training is an information-heavy pastime.

So.

This is normal. The OP probably isn't overtrained yet, just overcooked. What one does in his situation is take 2 days off, then go out on the bike, warm up, and hit a steep hill. Does HR come up normally?
Yes: You're good to go for now.
No: pedal easy on the way back home, take another day off, try it again.
Doesn't work again, add one day to the OFF period, try it again.
Repeat the above until you get a Yes.

He should have started doing this a month ago or so, but didn't know any better. Hopefully he can get it fixed without taking a long period off the bike. Probably can.

It's not a cardiologist thing. They don't know anything about it. They're doctors, and their correct attitude is, "If you're not sick or diseased, get out of my office, you're taking up time that I could use treating people who need it."

The fact that the OP is riding his bike fine, not seeing Afib, just not fast anymore argues for the cardiologist's point.

Been there, done that several times, got it fixed, try not to do that anymore.