Could Your Smartwatch Detect a Dangerous Heart Rhythm?

 

Smartwatches have come a long way from simply counting steps and buzzing with reminders. Today, many of them claim to monitor your heart and even detect serious rhythm problems. But how much can these devices really tell you? And more importantly, when should you take their alerts seriously?

What Smartwatches Can (and Can’t) Detect

Several popular smartwatches now come equipped with sensors that continuously track your heart rate and offer features like EKG (electrocardiogram) recordings. These tools can pick up irregular heart rhythms, such as:

• Atrial fibrillation (AFib)
• Tachycardia (fast heart rate)
• Bradycardia (slow heart rate)

Some devices will also flag “inconclusive” or “unclassified” rhythms, prompting you to follow up with your provider.

But here’s the catch: smartwatches aren’t diagnostic tools. They can only detect specific patterns, not the cause behind them. For example:

• They can’t always tell benign skipped beats from serious arrhythmias.
• They won’t detect ventricular arrhythmias or rare conduction disorders.
• Movement, poor contact, or skin conditions can throw off the results.

Consider these devices as an early warning system, rather than a substitute for a medical evaluation.

How Reliable Are Wearable ECGs?

Smartwatches have come a long way in helping people identify heart rhythm problems, such as atrial fibrillation (AFib). Thanks to built-in sensors and ECG features, some models can give you real-time feedback about your heartbeat, but how accurate are they?

Most smartwatches, including Apple, Fitbit, Samsung, and Garmin, use a light sensor called PPG (photoplethysmography) to track your heart rate. Many now also offer on-demand ECGs, which record a 30-second electrical snapshot of your heart rhythm using the watch’s electrodes. This combination gives them a surprising level of accuracy.

In the Apple Heart Study, which included over 419,000 people, about 0.5% of users received an irregular pulse alert. Of those who completed follow-up testing, 84% were confirmed to have atrial fibrillation.¹

The Fitbit Heart Study yielded even better results, with a positive predictive value of 98.2%, indicating that nearly all alerts were accurate.² Another study using the Samsung Galaxy Watch Active 2 found that when the on-demand ECG was used alongside the heart rate sensor, the watch was over 96% accurate in detecting AFib, and its ability to correctly rule out people without the condition was over 99%.²

Still, it’s important to know the limits. Most smartwatches only record your heart rhythm for short periods, which can miss brief or occasional episodes. While smartwatches are quite effective at detecting AFib, they’re not as reliable for identifying other rhythm issues, such as atrial flutter, supraventricular tachycardia, or heart blocks.

If you’re using a newer smartwatch and it detects an irregular rhythm, it’s worth taking seriously, especially if you’re over 65 or have risk factors such as high blood pressure or sleep apnea. However, regardless of what your watch indicates, always consult an electrophysiologist for accurate testing and guidance. Your instincts, paired with unusual symptoms, are a better indicator than any smart device.

When to Bring Your Smartwatch to Your Doctor

If your smartwatch flags an irregular rhythm, it’s worth following up when:

• You’re feeling symptoms like palpitations, dizziness, shortness of breath, or chest discomfort
• You receive multiple alerts over several days
• You have risk factors like high blood pressure, diabetes, sleep apnea, or a family history of heart problems

Bringing your watch data to your cardiologist or an electrophysiologist can provide a helpful starting point so that they can recommend:

• A medical-grade EKG or Holter monitor
• Further testing to assess rhythm, structure, or electrical conduction
• Lifestyle or medication changes, if needed

Smartwatches are changing the way we interact with our health. While they can’t replace medical tests, they can play a role in early detection. So, if your wrist is buzzing with alerts or your heart “just feels off,” don’t guess. Get it checked out.

Dr. Tordini, an electrophysiologist at Florida Medical Clinic Orlando Health, specializes in diagnosing and treating heart rhythm disorders. Whether your symptoms are detected through a smartwatch reading or just a gut feeling, she can help you make sense of what your rhythm is saying.

1. Perez, M. V., Mahaffey, K. W., Hedlin, H., Rumsfeld, J. S., Garcia, A., Ferris, T., Balasubramanian, V., Russo, A. M., Rajmane, A., Cheung, L., Hung, G., Lee, J., Kowey, P., Talati, N., Nag, D., Gummidipundi, S. E., Beatty, A., Hills, M. T., Desai, S., & Granger, C. B. (2019). Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation. New England Journal of Medicine, 381(20), 1909–1917. https://doi.org/10.1056/nejmoa1901183.
2. Mohamoud, A., Jensen, J., & Buda, K. G. (2024). Consumer-grade wearable cardiac monitors: What they do well, and what needs work. Cleveland Clinic Journal of Medicine, 91(1), 23–29. https://doi.org/10.3949/ccjm.91a.23030.