5 What Is the ECG Feature Exactly?
The ECG app lets users take easily an electrocardiogram using their Apple Watch. By way of onboard sensors, the Apple Watch ECG app can capture a user’s cardiac rhythm and detect certain heart-related problems, like irregular or skipped heartbeats. Notably, the Apple Watch Series 4 is the first consumer-facing device to feature an ECG capability (without a prescription).
There are some concerns about reliability, and Apple notes that it does not detect heart attacks, blood clots, strokes or other dangerous conditions.