As the user touches the Digital Crown, the circuit is completed and electrical signals across their heart are measured. After 30 seconds, the heart rhythm is classified as either AFib, sinus rhythm, low or high heart rate, or inconclusive.
The ECG app’s ability to accurately classify an ECG recording into AFib and sinus rhythm was validated in a clinical trial of around 600 participants. Rhythm classification from a gold standard 12-lead ECG by a cardiologist was compared to the rhythm classification of a simultaneously collected ECG from the ECG app.
In the study, 87.8 percent of recordings could be classified by the ECG app.
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Irregular Rhythm Notification
Using the optical heart sensor in Apple Watch Series 3 or later, the irregular rhythm notification feature occasionally checks the user’s heart rhythm in the background for signs of an irregular heart rhythm that appears to be AFib and alerts the user with a notification if an irregular rhythm is detected on five rhythm checks over a minimum of 65 minutes.
With over 400,000 participants, the Apple Heart Study was the largest screening study on atrial fibrillation ever conducted, also making it one of the largest cardiovascular trials to date.
To enable these heart features, customers are taken through an onscreen setup that includes details about who can use these features, what the features can and cannot do, what results in users may get, how to interpret those results, and clear instructions for what to do if users are feeling symptoms that require immediate medical attention.
