A few days ago Fitbit added an ECG app to the Fitbit Charge 5, even as we were reviewing this device. It’s quite a big deal for a tracker but it’s not the first time we’ve experienced it on a wearable; that happened during a product deep-dive during the launch of the Apple Watch Series 5 in 2019. While the ECG feature first debuted on the Apple Watch 4, it rolled out in India with the Series 5 after approvals from regulatory authorities. So, what is the ECG feature on a smartwatch all about?

ECG, demystified: an electrocardiogram (ECG or EKG) is a test that records the timing and strength of the electrical signals that make the heartbeat. The ECG app measures these pulses to get your heart rate and see if the upper and lower chambers of your heart are in rhythm. If they’re out of rhythm, that could be AFib or atrial fibrillation, a form of irregular rhythm. We’ll add a quick word of caution that most wearable manufacturers will endorse. An ECG reading on your wrist is not 100% accurate; treat it as a point of reference or an input for your doctor if at all.  Currently, the Apple Watch (Series 4 onwards), Fitbit Sense and Fitbit Charge 5 are among the wearables that offer an ECG app on your wrist. Samsung’s Galaxy Watch 3 and 4 are equipped with the ECG feature but it hasn’t been rolled out in India officially. You can install a developer option at your own risk. 

Read between the lines: the Apple Watch’s detailed report breaks down information to include some key readings. There’s sinus rhythm that indicates that your heart is beating in a uniform pattern between 50 and 100 BPM. It happens when the upper and lower chambers of your heart are beating in sync. AFib is the most common form of serious arrhythmia or irregular heart rhythm. The latest version of Apple’s ECG app can check for AFib between 50 and 150 BPM. A low or high heart rate (under 50 BPM or above 150 BPM in the latest version of Apple’s ECG App) affects the ECG App’s ability to check for AFib.

How is it measured: Wearables like the Apple Watch generate a single-lead (or Lead I) ECG. This is in contrast with a standard 12-lead ECG at a doctor’s clinic that records electrical signals from different angles in the heart to produce twelve different waveforms. The Apple Watch measures a waveform similar to one of those twelve waveforms. This also means that it can’t identify conditions like heart attacks. Doctors use single-lead ECGs to get a closer look at the underlying rate and rhythm of the heart. 

Quick tips to measure: most wearables take a 30-second reading that involves placing one or more of your fingers on the watch. For instance, the Apple Watch and Samsung’s Galaxy Watch require you to place one finger on the crown or a button while Fitbit’s Sense and the Charge 5 need you to place two fingers on the corners and sides respectively. It’s best to rest your arms or in your lap when you record and make sure your wearable is not too tight or loose. Stay calm and make sure your wrist and wearable are sweat free. Keep a distance from any devices plugged in for charging to avoid electrical interference. But most of all, you should find the balance between staying relaxed and yet not move around too much. You don’t want your anxiety to impact readings, do you?