Apple Watch ECG app

Apple's long-awaited ECG app is coming to Apple Watch Series 4 today as a free update. With it, you can take a reading of your heart's rhythm using the electrodes in the Series 4 to check for irregularities.

Additionally, watchOS 5.1.2 includes onboard notifications when a heart rate reading determines an irregularity. Through normal heart rate tracking, Apple Watch Series 1 through Series 4 will also check for signs if irregular heart rhythm that could be related to AFib and alert you with a notification if it detects five irregular heartbeats across 65 minutes.

Apple Watch ECG app

Apple notes that AFib, or atrial fibrillation, is one of the most common forms of irregular heart 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. The CDC estimates AFib can affect up to two percent of the younger population and nine percent of those 65 years and older in the US.

Apple performed a clinical study of about 600 participants to confirm Apple Watch Series 4's ability to successfully read heart rhythm.

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. The study found the ECG app on Apple Watch demonstrated 98.3 percent sensitivity in classifying AFib and 99.6 percent specificity in classifying sinus rhythm in classifiable recordings. In the study, 87.8 percent of recordings could be classified by the ECG app.

The ECG app and irregular heart rhythm notification feature will roll out across Apple Watch through the watchOS 5.1.2 update today.

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Once updated, you'll be taken through an onscreen setup that will detail what the features can and can't do, how to interpret your results, and instructions on how to seek help if you're feeling symptoms that require medical attention.