Hi there. I was a competitive runner, snowshoer, and did a lot of hard cycling. I was in the Canadian Armed Forces for 30 years, always fit, well-looked after for dental hygiene and general health, always vaccinated before deployments oversees. I developed atrial fibrillation (AF) suddenly near the end of a 10 km maintenance run. Long story short, I had all the usual tests, none turned up anything. The last diagnostic left in the list was an overnight sleep lab ( a polysomnography with a gazillion leads and machines blinking at me all night. Fortunately, I slept well for about six hours). Or....so I thought. The result that was fed to me ten days later was that I have severe sleep apnea. Who knew?!

Is your arrhythmia determined yet? Chances are that it is either PVCs (premature ventricular contractions(, PACs (premature atrial contractions), or AF. It might also be SVT, or supra-ventricular tachycardia, but the tachyarrhythmias are still in sinus rhythm...they're just quite a bit faster than necessary, often well above 130 BPM even at rest. A Holter monitor worn for several days, or a loop recorder, or maybe even an ECG while your heart is acting up one day, will determine which of those it is.