Question: how to do a ecg on apple watch 4?
Answer: Make sure that your Apple Watch is snug and on the wrist that you selected in the Apple Watch app. ... 
Open the ECG app on your Apple Watch.
Rest your arms on a table or in your lap.
With the hand opposite your watch, hold your finger on the Digital Crown. ... 
Wait. ... 
Tap Save to note any symptoms, then tap Done.