Cedars-Sinai Blog

Can a Smartwatch Save Your Life?

Checking Heart Rate on a smart watch

If you find yourself in a group of five people, one member of this quintet is likely to be wearing a smartwatch or fitness tracker, according to a Pew Research Center survey.

If this person starts experiencing atrial fibrillation (AFib), the device on the wearer's wrist can detect this most common type of abnormal heart rhythm and then document the event by conducting an electrocardiogram (EKG). These devices can prove lifesaving because an estimated 15% to 20% of all strokes in the U.S. are directly linked to AFib.

"Detecting, monitoring and recording AFib is the big breakthrough area that I see as a very useful tool."

The technology behind smartwatches and fitness trackers has advanced significantly over the last decade, but important questions remain. What are the verified heart-monitoring capabilities? How reliable is the AFib data they produce? Are there certain types of people who could most benefit from wearable tech?

To answer these and other questions, we tapped the expertise of Dr. Michael Shehata, a cardiac electrophysiologist and associate professor in the Cedars-Sinai Department of Cardiology. Dr. Shehata is also director of the Interventional Electrophysiology Laboratory and the Clinical Cardiac Electrophysiology Fellowship Training Program at the Smidt Heart Institute.

What are the heart-related capabilities of the latest smartwatches and fitness trackers?

Dr. Michael Shehata: I think the capabilities that are the most developed and validated are measuring heart rate as well as blood oxygen levels, and detecting atrial fibrillation. Heart rate is the number of times the heart beats per minute. While what's considered a normal heart rate varies from person to person, if your resting heart rate is much higher than average, or if your low maximum heart rate is significantly lower than average, this could be a sign of underlying heart disease.

Current devices also can measure blood oxygen levels, which is the amount of oxygen circulating in your blood. Low blood oxygen levels can damage organ systems, especially the brain and heart. Detecting, monitoring and recording AFib is the big breakthrough area that I see as a very useful tool.

Michael M. Shehata, MD

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Given that atrial fibrillation is the big breakthrough area, how reliable is the AFib data these devices produce?

MS: They're very good at not just detecting the presence of atrial fibrillation, but also at continuously recording an EKG strip of heart rhythms and then compiling that data so you can see the level of AFib a patient is experiencing.

The Apple Watch, for example, can mirror the data produced by medical-grade devices such as KardiaMobile 6L, by using light-based technology that analyzes pulse patterns to determine if they're consistent with atrial fibrillation. If they are, the smartwatch alerts the wearer and suggests seeing a healthcare provider.

The smartwatch also prompts the wearer to activate the EKG function, which can confirm AFib. The EKG strip can be recorded as a PDF and emailed to the person's doctor or uploaded into the individual's electronic medical record. It's a very convenient way for patients to directly engage in their care and gather data that's very useful for their physicians.

Another advantage of these devices is they can be worn continuously and track how often AFib is occurring, including silent episodes that aren't accompanied by symptoms, including irregular heartbeat, heart palpitations, lightheadedness, extreme fatigue, shortness of breath and chest pain. The accumulated data can help inform therapeutic decisions, such as prescribing a blood thinner.

Are there certain types of people who could most benefit from wearing these biomedical bands?

MS: These devices are particularly useful in patients where AFib is suspected but hasn't been verified. For patients diagnosed with atrial fibrillation, smartwatches and trackers are a good way of monitoring if their treatment—such as antiarrhythmic drugs or surgical ablation therapy—is reducing AFib.

Data from these devices also can be useful for someone who's reluctant to take a blood thinner, but—once they can be shown how often they're experiencing AFib—may feel more comfortable taking the medication.

Another group that could benefit are those who've had a stroke but don't know if it was caused by atrial fibrillation. A smartwatch or fitness tracker can confirm or rule out AFib, which can help inform treatment.

Have smartwatches and fitness trackers morphed into mainstream medical devices? If so, are you prescribing them to your patients?

MS: I wouldn't say I'm prescribing smartwatches or trackers, but some of my patients
have these devices and aren't aware of their capabilities. I will explain that their smartwatch can confirm and monitor AFib, and then I can review that data. Most of my patients are open to putting their smartwatches to work in this way.

I'm becoming increasingly comfortable with using these devices—not as the sole means of confirming or monitoring AFib—but as a good way to get a snapshot of what's going on. I'm finding that the data from these devices is largely reliable.

Do smart watches and fitness trackers have weaknesses or limitations?

MS: They certainly aren't infallible. Their AFib findings can be inconclusive, or there may be a misdiagnosis.

Also, if there's poor contact between the watch or tracker and the wearer's skin, which can prevent the optical sensor from working properly, then the data isn't going to be good. It's also important that people understand that these devices can't assess a person's risk of having a heart attack, heart failure or a stroke.

What else should people know about using these devices to monitor AFib?

MS: It's important to remember that the data these devices produce must be read and analyzed by a physician who's used to looking at EKGs.

Smart wearables are jampacked with technology, but the expertise of a skilled provider is still needed for data interpretation and development of a treatment plan, and that precisely describes the clinicians at the Atrial Fibrillation Clinic. That's what my patients turn to me for—they're not going to just trust what a watch tells them, especially in relation to a condition as consequential as AFib.

As these devices continue to evolve, they may have a role at our clinic, but it would be as just one of a multitude of tools we employ to provide the best care to our patients.