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Just weeks after seeding its watchOS 5.1.1 software update to the public, which primarily patched a bricking issue discovered in the initial build and introduced new emoji characters, the company on Thursday released its third (and arguably most highly-anticipated) update to watchOS 5: version 5.1.2, to the public.

Most notably, the 5.1.2 update enables Cupertino’s FDA-approved electrocardiogram (ECG) feature on Apple Watch Series 4 models in the United States. 

What Is an ECG?

An ECG is a very non-invasive medical test designed to measure the electrical activity of the human heart, and is most often employed by cardiologists, hospitals and medical centers to aid in the diagnosis of heart conditions like Atrial fibrillation (Afib).

ECG, which on Apple Watch Series 4 functions via strategically-placed electrodes built into the back of the wearable (in conjunction with its Digital Crown), enables users to carry out a “single-lead electrocardiogram” from the convenience of their wrist.

While the ECG mechanism is limited to Apple Watch Series 4 models, watchOS 5.1.2 brings to nearly all Apple Watch models (Series 1, 2 & 3) a useful new notification feature designed to inform wearers if they have an abnormal heart rhythm in the first place — which is among the most paramount symptoms indicative of Afib, and/or a host of other underlying health anomalies.

Other Notable watchOS 5.1.2 Features

watchOS 5.1.2 introduces new complications for the Infograph watch face on the Apple Watch Series 4, which take advantage of the model’s larger display and can be configured to incorporate shortcuts to apps like Mail, Messages, Maps, Apple News, Phone, Remote, and more.

The new software build also includes a handy on/off toggle for more easily controlling the wearable’s Walkie-Talkie feature directly from the watchOS control center.

According to Apple’s official release notes, watchOS 5.1.2 boasts the following new features, improvements and bug fixes:

• New ECG app on Apple Watch Series 4 (US and US territories only). 
• Allows you to take an electrocardiogram similar to a single-lead electrocardiogram.
• Can indicate whether your heart rhythm shows signs of atrial fibrillation—a serious form of irregular heart rhythm—or sinus rhythm, which means your heart is beating in a normal pattern.
•  Saves ECG waveform, classification and any noted symptoms in a PDF on the Health app on iPhone to share with your doctor.
• Adds the ability to receive an alert if an irregular heart rhythm that appears to be atrial fibrillation is detected (US and US territories only).
• Enables direct access to supported movie tickets, coupons, and rewards cards in Wallet when tapped to a contactless reader.
• Receive notifications and animated celebrations when you achieve daily maximum points in a day during an Activity competition.
• New Infograph complications for Mail, Maps, Messages, Find My Friends, Home, News, Phone, Remote.
• Manage your availability for Walkie-Talkie from Control Center.

How to Download watchOS 5.1.2

As of Thursday morning, and as with previous updates, watchOS 5.1.2 can be downloaded for free via the dedicated Apple Watch app on your iPhone by navigating to General > Software Update. 

(NOTE: Ensure that your Apple Watch has at least 50 percent battery remaining, that it’s resting on a charger, and that it’s within a 25-foot range of your iPhone before initiating the update.)