Further to the above: decyphering the letter from the cardio, it would appear that I have hyperexcitable atria, and I gather that spurious spikes are crossing the bundle of His* and "troubling" relaxation of the left ventricle. This is annoying, since it's exactly what the currently crocked El Prez suffers from, only he's reached the extreme phase.
I know of several cyclists who have this. Mostly they're col-chasers: I'm the first endurance rider I've heard of with it. However, long ago I was told by an anaesthetist that "we'll have you in here one day for a pacemaker. We get droves of cyclists needing them".
Just now the cardio wants to try BBs, but if they're too effective - and I know they would be - he wants me on an anticoagulant instead, and warns me of the risk of haematomata [sauce] if I fall off my bike. In future I'm only to ride on quilted roads.
Joking apart, it looks like the start of something major. Shit.
OTOH yesterday I did 149 km with 900+ metres of climbing at an average of 22.2 kph, so there's life yet. Need to find out how many seasons I can get in before the chopper.
* or Theirs if you want to be non-denominational