According to a report published in a medical journal, a patient's Apple Watch successfully detected a serious anomaly missed by diagnostic hospital equipment. However, when the individual pointed out ECGs matching the health issue in question generated by her wearable to doctors, it was apparent treatment was in order.
https://www.notebookcheck.net/An-Apple-Watch-is-credited-with-saving-yet-another-user-from-an-acute-heart-condition.463697.0.html