It says the irregular rhythm detector isn't for people who've been diagnosed with atrial fibrillation. And both the EKG and heart rhythm function are "not intended to replace traditional methods of diagnosis or treatment." As The Washington Post has reported, some cardiologists worry people taking Watch EKGs could result in a flood of unnecessary office visits by healthy people. The heart sensors can let people with heart conditions or anxiety know when they might need to take it easy. Margery Widroe, 80, who's been using a Series 3 Apple Watch for a few months, recounted to our group a recent incident when she was at the grocery store and her Watch alerted her to a high heart rate.