Wish I had this problem. Instead, I get spontaneously younger (based on 220 minus age) for no reason and sometimes for long periods.
Last weekend at the Red Bull Timelaps I was thoroughly enjoying myself in my first turn when my HR monitor started beeping at me. I've set it to go off at 170bpm so I can keep an eye on things. I certainly wasn't putting in 170 bpm of effort at the time.
So I assumed it was caffeine (Red Bull event, after all...) and to be honest a lot of adrenaline: there were some VERY serious cyclists on that course. On my first lap I went wide on a narrow downhill left-turn and got a LOUD shout from behind. Turns out I'd almost skittled Alex Dowsett. My bad.
Anyway, for the next few hours I had the jitters that usually accompany my high HR problems. Sat chatting to a team mate in the hospitality tent my HR was 120bpm. The rest of the event was spent managing it until fatigue took over the duty and no matter how hard I tried the alarm wasn't going off! That's another thing I learned.
Actually, there were so many lessons learned from that event I'll write it all up in another post. Just like old times.