I have worn an Apple Watch for the past 5 years. 4 yrs ago, it alerted me to a highly variable heart rate, so I saw a cardiologist, underwent a stress test and passed it OK. Fast forward to Thanksgiving 2021, my watch alerted me to possible AFIB 3 nights in a row. I couldn’t get an appointment with the cardio Dr until January ‘22. AFIB confirmed in Feb and medication started (Eliquis & Metoprolol). I monitor my status daily using my watch, and it is very consistent in telling me I’m in AFIB when I can feel the palpitations. So, I believe the readings are accurate.