Apple (AAPL) announced results of a large study that used Apple Watch to screen for atrial fibrillation, a common arrhythmia. The watch diagnosed atrial fibrillation in only 34% cases, so it missed it in 66% cases.
I have asserted it repeatedly that too much hype is being made over the Apple Watch as being a substitute for EKG. An EKG uses 12 leads (one over each limb) and rest on the chest. The Apple Watch is just equivalent to one limb lead for an EKG.
So, the Watch can detect and give an alarm for an arrhythmia in some cases, but it will never be 100% accurate in diagnosing all arrhythmia. It is not possible as one lead cannot match the accuracy of 12 leads of an EKG.
The study also showed many false positives, so the watch has low specificity as well. It's still not an ideal instrument to exclude arrhythmia.
TAM: approx. 6 million Americans with atrial fibrillation. Yes, it is common and I have managed it in my clinical practice.
You don't need a watch to give you an alarm for arrhythmia. If you feel your heart is racing fast, just put a finger on your pulse (I am assuming that you know how to check your pulse). If you cannot feel the pulse or feel it is irregular, just call 911 to take you to the ED.
There's no need to spend $400 to buy an Apple watch just to detect arrhythmia. As I mentioned above, you just need to learn how to check your pulse. This opinion comes from 5 years of medical school and over 18 years of clinical practice, including managing atrial fibrillation.
If you are buying Apple watch for measuring steps, calories burn, etc., Fitbit has better devices and much cheaper and simpler. I use a Fitbit device that does not have a watch function. I don't need a watch. My iPhone is enough for that.
Dr. Bhatt, Cardiologist from Harvard/Brigham (who is also a paid salesman for Amarin's Vascepa), I would appreciate it if you show your financial relationships with the companies whose products you are providing your expert comments on. You are required by law to provide these disclosures.
Full disclosure: I bought an Apple watch 4 years back and was very enthusiastic but never used it, so gave it to my Dad, who apparently is very happy wearing it as a piece of jewelry.
No position in AAPL. Not investment advice.