Dr. Sanjay Gupta, CNN:

The US Centers for Disease Control and Prevention estimates that as many as 6.1 million Americans are living with a-fib, and that number is only expected to increase as the population grows older. Apple’s hope is that with the single-lead ECG available anytime you are wearing your watch, you have a better chance at screening for atrial fibrillation at the time it is happening.

This is a well-written, easy to understand first look at the just-released Apple Watch’s ECG feature. It’s full of little details, such as:

The new Apple Watch features are cleared, but not approved, by the US Food and Drug Administration. It may seem a subtle point, but for something to be approved by the FDA, it is subjected to much more rigorous testing and data collection. Clearance is typically given to medical devices that have been determined to be substantially equivalent to another legally marketed device — an easier hurdle to cross.

And:

According to clearance letters sent by the FDA to Apple on September 11, the app is intended for use only in people ages 22 and up, whom the FDA considers adults. The irregular rhythm notification feature is not intended for use in people who have been diagnosed with a-fib, who should be under a doctor’s care.

There are already lots of stories floating around about people who have tried this feature out and caught a potentially life-threatening condition. I have yet to see a downside emerge, a rash of false positives for example.

So far, this seems like a hugely positive rollout. Time will tell, obviously, but I like what we’ve seen so far and I’m looking forward to more features like this from Apple and the Apple Watch and Health teams.