(Insert the usual disclaimer about receiving medical advice over the internet. I'm not worried about telling you what I'm about to tell you, because I trust you are under a competant physician's care, and are following that physician's recommendations solely, and that you'll use any information given to you here as just that...information, not medical advice that you should follow.)
It doesn't sound that unusual to me, Francois. Neither the high HR, nor the "skipped beats" after decreasing training so much. There is a theory, at least among local cardiologists, that people with very high exercise levels tend to have a larger left atrium. As the athlete either gets dehydrated (see ultra-endurance races, and the number of people that get arrhythmias) or decreases training volume severely, the enlarged Left Atruim decreases in volume and therefore, size. The more tightly bunched cells tend to be more irritable as they get closer to one another, and arrhythmias follow.
Atrial fibrillation is one of the potential problems...and is debilitating to many high level athletes. It can also be dangerous due to clot formation in the atria, which can then embolize.
If you just feel a few "skipped beats", that's not A-fib. It's probably just Premature Atrial Contractions, or, PAC's. Very common, especially in young people, especially when combined with dehydration, or in athletes with greatly decreased training volume, and in those with stimulant useage (such as caffeine). Until you find out exactly what is going on (and you may not...there's no guarantee your tests will be definitive), avoid caffiene entirely, as well as any other stimulants, and try and get as much rest as you can. If I were you, and I am not, I would take an aspirin tablet or two each day until I got my results...it makes the clotting mechanism a little less effective, i.e., one will bleed more if one gets a cut, but it's cheap insurance that will increase the amount of time that A-fib could be withstood before a potentially harmful clot were to form.
Unless advised otherwise by your doctor, you should be able to do some training. If you get a very rapid irregular HR, that is probably A-fib, and it needs attention quickly as mentioned above, but, it won't kill you!
Most of the time, nothing bad is found in people in your situation. However, you are doing the prudent thing by being checked out. Try and chill out, you're probably fine, and responding in a not-uncommon way to the situation in which you are describing.
Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)