Needs to be a Series 4 or 5 Apple Watch (not a 3 for EKG). Also know the limitations-doesn’t check all the time for AFIb (& checks are test). Also check the settings for high & low heart rate...those only check when at rest & HR has to stay at/below the set levels for 10 minutes straight. Best is to run an EKG if things feel “off”. My BP monitor was showing irregular heart rates on multiple occasions on 3/10/19. Plus was getting very short of breath & couldn’t stay on my feet. Ran 9 EKGs & 7 came up AFIb. Only got 1 irregular heart rate warning from the Watch after I gave up for the day & decided to just stay in my recliner. Had appointment with my EP on 3/15 & showed him EKGs. Was put on meds for rhythm control & also Eliquis. Had ablation done on 7/29/19 & now feeling the best I have felt in years. Seeing him on 2/14/2020 & the plan is for a loop recorder to monitor so I can stop taking Eliquis.