The Apple Watch’s ECG features are live

Apple Watch
Each ECG recording is saved in an iPhone app and can be shared as a PDF with physicians. (Apple)

The new Apple Watch’s electrocardiogram capability has gone live, available as a free software update that allows for wrist-based ECGs on-the-go.

The watch can now also track a person’s pulse in the background and send the wearer a notification if it detects what could be atrial fibrillation, the most common form of irregular heart rhythm.

The notification feature will also work with heartbeat sensors on earlier versions of the Apple Watch, alerting the user if an irregular rhythm is detecting five times or more over 65 minutes.

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Designed for people aged 22 and over, the ECG app and irregular rhythm notification feature received de novo clearances earlier this September. Apple cites CDC estimates that atrial fibrillation can affect up to 9% of people over the age of 65 in the U.S. and up to 2% of the younger population.

RELATED: New Apple Watch receives FDA clearance for built-in ECG

“The role that technology plays in allowing patients to capture meaningful data about what’s happening with their heart, right when it’s happening, like the functionality of an on-demand ECG, could be significant in new clinical care models and shared decision making between people and their healthcare providers,” said Nancy Brown, CEO of the American Heart Association, in a statement.

Using electrodes built into the back of the watch and its crown, the wearer completes a circuit while holding it with their opposite hand, allowing the watch to send electrical signals across their heart to take a 30-second ECG akin to a single-lead reading.

The app then classifies the heartbeat reading as a normal sinus rhythm, atrial fibrillation or inconclusive. Each recording is saved in the iPhone app and can be shared as a PDF with physicians.

“The idea that wearables can be used by both patients and their healthcare providers to manage and improve heart health holds promise and should also be approached with caution to ensure information and data are used responsibly and in concert with other evidence-based tools and guidelines,” said C. Michael Valentine, M.D., president of the American College of Cardiology, in the statement.

The ECG app was evaluated in a clinical trial of about 600 participants, comparing their sinus rhythms to simultaneous 12-lead ECGs performed by a cardiologist, Apple said. The study found that the Apple Watch demonstrated 98.3% sensitivity in classifying atrial fibrillation and 99.6% specificity.

The much larger Apple Heart Study, screening over 400,000 participants for atrial fibrillation, also evaluated the watch’s irregular rhythm background notification feature. In a substudy of participants that received notifications—while wearing both the watch and an ECG patch—80% showed atrial fibrillation readings on the patch, while 98% showed either atrial fibrillations or other arrhythmias.

“We are confident in the ability of these features to help users have more informed conversations with their physicians,” said Sumbul Desai, M.D., Apple’s VP of health, in the statement. “With the ECG app and irregular rhythm notification feature, customers can now better understand aspects of their heart health in a more meaningful way.”

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