You've probably heard or read a story about someone who was first alerted about their irregular heartbeat by their watch — specifically, a smartwatch with ECG capability built in. With an increasing number of people wearing these devices, the accounts of how they helped someone detect a health issue are becoming more and more common.

But these stories can sound almost too good to be true.

It's easy to believe that a smartwatch can improve your overall health — that's why you wear one. But can it really warn you of a heart condition silently developing?

It's just a watch, after all.

According to Dr. Maged Amine, an interventional cardiologist at Houston Methodist, it turns out that smartwatches with ECG capability can play a role in screening for and monitoring at least one heart condition — atrial fibrillation (AFib), one of the most common types of arrhythmia. In fact, through its Medical Device Development Tools program, the FDA recently designated Apple's AFib History Feature as a qualified tool for assessing estimates of AFib burden within clinical studies.

"AFib occurs when the rhythm of the heart becomes irregular, usually too fast," says Dr. Amine. "This leads to reduced function of the heart. It's a common heart condition that is often asymptomatic, meaning it doesn't always manifest with obvious symptoms. Unfortunately, the first presentation of AFib is often having a stroke due to blood clots in the heart."

In fact, AFib increases a person's risk of having a stroke five-fold, making it one of the leading causes of stroke.

"Now, with people wearing devices with built-in ECG capability all day, every day, we're seeing the emergence of a convenient way to broadly screen for AFib," explains Dr. Amine. "And this technology can also help improve how we monitor this condition long-term, too."

What is an ECG and what is its role in detecting AFib?

"Ideally, we catch AFib before it leads to stroke," explains Dr. Amine. "And whether performed in a doctor's office or via a portable device worn at home for a few days, we've used electrocardiogram (ECG) to help detect AFib for decades."

An ECG measures how fast the heart is beating, providing clues whether a person's heart rhythm is normal or irregular. Traditionally, this test uses electrodes attached to your chest and other parts of your body. The information collected by these electrodes is sent to a computer, then reviewed by your doctor to determine whether your heart rhythm might be irregular.

Your doctor may recommend an ECG if you're noticing heart palpitations, chest pain or shortness of breath as well as the more subtle signs of AFib such as lightheadedness and extreme fatigue. An ECG is also part of the screening practice for those who are at high risk for heart disease or have a family history of heart disease. (Related: 5 Commonly Ordered Heart Tests & What They Show)

"But, given that AFib is fairly common and can present without symptoms, a simpler and more broad way of screening for it would be very beneficial — helping catch AFib in people who are asymptomatic and not eligible for traditional ECG screening," adds Dr. Amine. "The thought is that smartwatches with ECG capability could perhaps help fill this gap."

There is a precedent — not with a smartwatch, but with a device that functions very similarly. A 2017 study assessing whether regular use of an at-home ECG device could more effectively help screen for AFib found that it uncovered more cases than standard screening guidelines.

Are smartwatches with ECG capability really smart enough to detect AFib, though?

The ECG technology in a smartwatch uses LEDs flashed against your skin to detect blood flow and measure your heart rate. Sensors collect this information and algorithms process it to make sense of your heart's rhythm. Your smartwatch takes these measurements throughout the day, and, if an irregular rhythm is detected, it sends you an alert.

Because it's so different from the traditional ECG technology used in the clinic, you might be skeptical about whether what's crammed inside a tiny watch is truly sophisticated enough to detect if you're in AFib. But Dr. Amine gives these devices high marks.

"The ECG technology in smartwatches is very accurate," Dr. Amine explains. "And people have options with these watches now. The Apple brand was the leader in this technology, but other brands have followed, including Fitbit and Samsung."

Their accuracy and utility haven't gone unnoticed. Certain series of smartwatches made by the brands mentioned above are FDA-approved to help users identify signs of AFib.

If you wear one of these devices and get an alert, don't brush it off. Your next step is to check in with your doctor. He or she can order the tests needed to confirm or rule out AFib.

ECG-capable smartwatches can also help better monitor AFib

The implications of having on-demand ECG technology in a personal device that's worn frequently by many people is probably most readily apparent for screening of AFib.

"But these devices can also be very helpful for the long-term monitoring of those already diagnosed with AFib, too," explains Dr. Amine.

That's because AFib, unfortunately, can come and go. This means ECGs aren't just used for the initial detection of AFib, they're also an important part of regular checkups after treatment — used to help catch it in case it returns.

"What's been missing is a convenient way to continue monitoring a person's heart very closely so that we're able to quickly detect AFib if it comes back before their next checkup," says Dr. Amine.

In some cases, an implantable ECG device is used to monitor a person's rhythm for several years after treatment. But implanting this device is a medical procedure, and Dr. Amine points out that this option isn't right for everyone.

"Amazingly, these smartwatches are almost as accurate as implantable ECG devices — with the added benefit of not requiring a medical procedure," Dr. Amine adds. "They're amazing devices."

Additionally, Dr. Amine points out that smartwatches might eventually help ease the reliance on blood thinners after AFib treatment.

"Treating AFib usually includes taking medications that help control the heart's rhythm or undergoing a procedure called ablation therapy," explains Dr. Amine. "It also almost always includes using blood thinners to reduce the risk of stroke. Once we get someone out of AFib and back into a normal rhythm, they often wonder when they can get off blood thinners. It's an important question to consider since there are risks to taking these medications."

But, there's risk in stopping blood thinners too soon since it leaves a person more vulnerable to stroke if AFib does return — especially if it returns without symptoms. But perhaps smartwatches may someday help safely discontinue blood thinners in some people.

"If we can rely on these devices for long-term monitoring of AFib, we can use them to help inform if and when we should re-initiate treatment," Dr. Amine adds.

A smartwatch doesn't substitute the healthy lifestyle behaviors that help manage AFib, though

Smartwatch aside, the best way for people with AFib to manage their condition is to regularly check in with their cardiologist and prioritize the healthy lifestyle behaviors proven to reduce the chances of AFib, such as:

• Exercising
• Getting plenty of sleep
• Avoiding excessive alcohol
  
  

"Your smartwatch can be an added layer of protection, though," says Dr. Armine. "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. I hope someday this can be something we prescribe to patients to help monitor AFib. These devices are costly, but they are powerful."

(Related: Can a Fitness Tracker Help Improve Your Heart Health?)