Side note, the ECG function is on demand, single lead, and only detects afib. If you are hoping to replace a 12 lead or detect MIs save your money.
Apple is a FDA cleared device as a one lead ECG
The wording "only detects fib" is technically incorrect for others that may not understand it. The Apple Watch will only
warn of AFIB.
However being an ECG it will record
any irregular heartbeat and since it records your heartbeat which you can show your doctor to investigate further.
So it will record any irregular heart beat that you can show to your doctor but the watch itself software is only programmed to warn of A-Fib which makes sense.
More or less, if you like me wake up in the middle of the night with these strange sensations that you have been trying to explain to your doctor and he "blows it off as nothing" because the ECG in his office shows ok (which many do not know is only a 15 or 30 second snapshot of your heart at the exact time the ECG is being run).... then ...
You can record you own ECGs at the actual time you are feeling it and show him (or make an appointment direct with a cardiologist) and show the recorded ECGs to the doctor from your cell phone, or do what I did and print them out from PDFs AND if you already have a cardiologist also do what I did and messaged with them and the PDFs of the ECGs from the watch.
The watch greatly speeded up my treatment by showing those ECGs ... an alert NP from my cardiologist had me come right in on a day my doctor was out of town. They hooked me up to a 24 (or 48 I forgot) Holter Monitor and confirmed an insane amount of PVCs over night I forgot at this point but was 20,000 I think, including short term v-tach.
Finally because of the watch this lead to an eventual cardiac ablation saving me from possible heart damage, follow ups and just a recent, less than a year ago EchoGram shows a very healthy EF score of 60
and now a regular heartbeat