However, the tech giant didn't make the feature available during launch and said it will be added via a future software update.
And now, with watchOS 5.1.2, Apple has finally enabled ECG feature on its latest wearable.
Here's all about it.
Apple Watch Series 4 finally gets ECG feature
What's new in the update?
The update enables the ECG functionality that can capture a live electrocardiogram using the smartwatch's built-in heart rate sensor and Digital Crown.
It also brings the new Infograph complications for apps like Mail, Maps, and Messages.
Further, the update lets you control Walkie-Talkie status from Control Center, updates the Wallet app for contactless readers, and adds new UI for Activity competition.
An overview of the ECG app
The ECG app (available in the US) lets you take an electrocardiogram and save its waveform in a PDF format to share it with your doctor.
Further, the official change log says "the app can indicate when your heart rhythm shows signs of atrial fibrillation - a serious form of irregular heart rhythm".
Notably, the new features have been given clearance by the FDA.
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Apple Watch Series 4: At a glance
To recall, the new Apple Watch features a 30% larger screen area than its predecessor and runs on a new S4 chipset which is twice as fast as the previous iteration.
Further, it has 50% louder speakers, an all-new Digital Crown with haptic feedback, and a repositioned microphone for reduced echo, and all-day battery life.
It is also compatible with previous generation Watch bands.
Apple Watch Series 4 takes your health seriously
The Apple Watch Series 4 comes with next-generation accelerometer and gyroscope that allow the device to detect hard falls and calls Emergency services after 60 seconds of inactivity.
Also, like mentioned above, an all-new electrical heart rate sensor and optical heart rate sensors can record an ECG via the ECG app.
There's also a Walkie-Talkie feature along with several health monitoring features.
Apple Watch Series 4: Pricing for GPS and Cellular models
The GPS model with Aluminum case starts at Rs. 40,900 for the 40mm variant, while the 44mm costs Rs. 43,900.
The GPS+Cellular variant with Aluminum case starts at Rs. 49,900 and Rs. 52,900 for the 40mm and 44mm options, respectively.
The GPS+Cellular model with Stainless Steel case starts at Rs. 67,900 for the 40mm variant, while the 44mm variant is priced at Rs. 71,900.