https://www.theverge.com/2018/9/13/17855006/apple-watch-series-4-ekg-fda-approved-vs-cleared-meaning-safe

Yesterday, Apple announced that the US Food and Drug Administration cleared two new features for the Apple Watch Series 4. One is an advanced method of monitoring the heart called an electrocardiogram (EKG), and the other is the Watch’s ability to detect and notify the user of an irregular heart rhythm. Both features will be available on the device later in 2018 (not at launch). The news sounds exciting, but there are some important caveats that limit how useful the new gadget will be.

First, the FDA clearance letters for both the EKG and irregular rhythm notification functions note that they are not intended to be used by people under the age of 22. The irregular rhythm feature is not intended for people who have previously been diagnosed with atrial fibrillation, which is one of the most common causes of an irregular rhythm. (In other words, this feature is best used by people who are already well.) And both letters specify that the apps are “not intended to replace traditional methods of diagnosis or treatment.” They might provide extra information and that information might be helpful, but they won’t replace a doctor’s visit.