Other than the ECG app, the heart features include irregular heart rhythm notifications on several Apple Watch models. Both the ECG function and the notifications could be included in the upcoming watchOS 5.1.2 update.

It's not clear why Apple is reportedly extending the return eligibility period -- the Food and Drug Administration is not requiring it to do so, an agency spokesperson told MacRumors. Engadget has contacted Apple for comment and we'll update this story if it responds.