Abnormal Heart Rate Detected Alerts - What exactly was detected?

I had similar issue, disappointed that no further info is available esp for em services if needed.

I have heart issues so not surprised at receiving message but much like yourself baffled as to why and no data to support 

Hey, everyone.

I got two or three of these alerts a while back - does anyone know if you can refer back to when the alerts occurred? I didn't record them manually and can't see a way of looking back to find out. Is the data stored somewhere? It'd be really helpful to know the dates.

I changed it last year to 150 and haven't seen that worrisome alert displayed again since then.

I'm replying to your suggestion of using 220 - age because it is not fully possible if the result ends in anything other than 0 because the HR widget automatically selects 0 as the final third digit after you select the first two digits.

Your heart rate must have gone over the default alert threshold of 100 bpm during a period of what the watch considers rest. That apparently can easily happen for me while playing video games until I raised the default to a higher value of 150 bpm. See rawveeda's answer above for the steps on the watch if you want to set your threshold higher. Good luck!

I am not a doctor so I can't say whether it's only appropriate to use 220 minus your age while working out. It seems to me though that if that rule of thumb is to determine your maximum heart rate then it should be nearly equally as relevant when otherwise active (ie is playing a videogame that raises your heart rate due to adrenaline rush considered resting?).

I know this is an older post but for anyone still wondering about this issue, I have a fenix 6 pro solar and the alert happened about 4 times in one week, and I noticed my heart rate was changing relatively regularly just when watching it on the display. Fast forward a week and I spent 6 days in the hospital for an arrhythmia caused by inflammation from a virus that attacked my heart! No kidding. 

Same here! So frustrating!

I have the same watch. My just went off too! It scares you! I checked my settings too, like yours mine was set at 100 also. Which I never set in the first place. So I understand where you are coming from. 

Well it happens to me today. I was working this morning and the garmin start with the alarm abnormal heart rate detected. I´m still surprised and confused my bpm was 93 and my bph 5400. I was sitting in a new place and I want to know what to do?