Starting today, the ECG app on Apple Watch Series 4 marks the first direct-to-consumer product that enables customers to take an electrocardiogram right from their wrist.

The irregular rhythm notification feature on Apple Watch can now also occasionally check heart rhythms in the background and send a notification if an irregular heart rhythm that appears to be atrial fibrillation (AFib) is identified. Apple worked with the Food and Drug Administration (FDA) for a number of years to receive De Novo classification for the ECG app and the irregular heart rhythm notification, making the features available over the counter.

Available today as part of a free update to watchOS 5.1.2, the ECG app and irregular heart rhythm notification feature will help users identify signs of AFib, the most common form of irregular rhythm. When left untreated, AFib is one of the leading conditions that can result in stroke, the second most common cause of death around the world.

New electrodes built into the back crystal and Digital Crown on Apple Watch Series 4 work together with the ECG app to enable Apple's customers to take an ECG similar to a single-lead reading. To take an ECG recording at any time or following an irregular rhythm notification, users launch the new ECG app on Apple Watch Series 4 and hold their finger on the Digital Crown. 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 or inconclusive. All recordings, their associated classifications and any noted symptoms are stored securely in the Health app on iPhone. Users can share a PDF of the results with physicians.

Using the optical heart sensor in Apple Watch Series 1 or later, the irregular rhythm notification feature will occasionally check 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.

watchOS 5.1.2 will be available for download today.