EKG

What is an electrocardiogram?

Your heart is a pump that keeps blood flowing, picking up oxygenated blood from the lungs, and bringing that oxygenated blood to all the muscles in your body. There is an electrical conduction system that regulates the various chambers of the heart to ensure that they are pumping in the correct order. An electrocardiogram, or EKG (sometimes also referred to as ECG), represents a recording of this electrical activity.

When these electrical signals are not functioning properly, it can cause the chambers in the heart to pump out of order. This can cause a condition known as Atrial Fibrillation, or AFib. This condition prompts individuals to get an EKG at a doctor’s office, and potentially be remotely monitored with a fitness tracker.

How is an EKG obtained in the doctor’s office?

An EKG is obtained at the doctor’s office by placing electrodes across your body to measure the electrical activity in your heart. These electrodes are small silver/silver chloride disks surrounded by a conductive gel, in order to amplify the signal. This is not a painful process, and one does not get shocked when getting a recording.

EKG Placement

The industry standard EKG is obtained in the 12-lead method. This means that 10 electrodes are placed in various locations: 6 across the heart, and 4 on your limbs (one for each arm and leg). It is called the 12-lead method because 3 of the 4 electrodes on your limbs each have a dual purpose in recording (the last electrode is a ground). Therefore, 3 electrodes with two purposes combined with the 6 across your heart make a total of 12 leads. You can measure the electrical activity across the pathways between each electrode, each one producing a different waveform. Collectively, a physician can get the whole image of all the electrical activity in the heart, and they can use this information to help support a diagnosis.

How does a fitness tracker obtain an EKG?

Most fitness trackers, such as the Apple Watch, follow a one-lead EKG method. An electrode is generally placed behind the fitness tracker so that it sits on top of your wrist. In order to “close the loop” and read the electrical activity across your heart, with your other hand, you have to touch the other electrode on the fitness tracker while taking the recording. This other electrode is generally placed on the watch crown (the dial on the side). This would be similar to getting one of the twelve waveforms that you would get if you were getting an EKG at the doctor’s office. Many of the fitness trackers will be able to tell you if this one graph is normal, or if there is an abnormality, it may classify the rhythm as AFib.

Can I trust the EKG data from a fitness tracker?

Quite a few studies have been published assessing the accuracy of EKG data from a fitness tracker. For example, this study indicates that the EKG data from an Apple Watch is a true positive rate of 95.5%, and a true negative rate of 97.1% compared to a standard 12-lead EKG. However, while this data is promising, the accuracy and results, should be taken with a grain of salt.

The FDA classifies many of these wearables as low-risk fitness monitors, therefore, they don’t have the same stringent regulations that are considered for other medical devices. The current regulations mean that these devices can pass as being safe, but the data produced may not be the most accurate. Furthermore, there still is a lack of consensus on these products because of the minimal amount of clinical trials.

With that being said, these devices do provide patients with another tool for taking their healthcare into their own hands. Dr. Maged Amine, an interventional cardiologist at Houston Methodist, states, “Your smartwatch can be an added layer of protection… It can provide your doctor with more information that can help guide treatment, as well as help you better monitor your condition and avoid visits to the ER.”

The EKG data from fitness trackers can provide great information such as whether your heart is functioning normally or in AFib, however, it may not detect all abnormalities. It can be used as a great tool, however, if you believe you are having a medical emergency, it’s best to call emergency services and visit your physician.

Which fitness trackers can do an EKG?

Apple: Apple Watch 8, Apple Watch 7, Apple Watch Ultra

Fitbit: Fitbit Sense 2, Fitbit Sense

Withings: ScanWatch, ScanWatch Horizon, Move ECG

This is for informational purposes only and should not be considered as medical advice. Go to the emergency room if you are experiencing a life-threatening medical emergency.

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Blog written by Amrit Bhatia.