TecnoOrange 
The electrocardiogram (ECG) is one of the most valued features of modern smartwatches, but also one of the most misunderstood. How to use the smartwatch ECG correctly isn’t difficult, but there are details most people ignore that make the difference between a useful reading and a useless one. Here’s everything you need to know.
Table of contents
Table of contents
What is the smartwatch ECG and what does it detect?
The smartwatch ECG is a simplified version of the 12-lead ECG performed in hospitals. Your watch has electrodes on the back of the crystal and on the digital crown (Apple Watch) or buttons (Samsung and others).
When you place your finger on the electrode, the watch measures your heart’s electrical activity between two points. It’s a single-lead ECG, sufficient to detect:
- Atrial fibrillation (AFib): Irregular heartbeat that can increase stroke risk.
- Normal sinus rhythm: Confirms your heart beats with regular rhythm.
- Bradycardia / tachycardia: Unusually slow or fast heart rate.
Important: The smartwatch ECG does NOT detect heart attacks, heart blocks, or other serious conditions. If you have chest pain, difficulty breathing, or feel unwell, call emergency services. Don’t rely on your watch for that.
How to take an ECG step by step
On Apple Watch (Series 4 or later)
- Open the ECG app on your Apple Watch.
- Sit down and rest your arm on a stable surface.
- Place the finger of your other hand on the digital crown for 30 seconds.
- Stay still and don’t talk during the measurement.
- The watch will show your result: sinus rhythm, atrial fibrillation, high/low heart rate, or inconclusive reading.
On Samsung Galaxy Watch (4 or later)
- Open the Samsung Health Monitor app.
- Sit down and rest your arm firmly.
- Place the finger of your other hand on the top button for 30 seconds.
- Stay calm and don’t move.
- The result will appear on screen and save to Samsung Health.
Common mistakes that ruin the reading
Most “inconclusive” readings are due to avoidable errors:
- Moving during measurement: Stay still. Any movement generates noise in the signal.
- Arm resting on soft surface: Rest your arm on something firm (table, rigid leg).
- Sweaty or cream-covered skin: Dry your wrist and the back of the watch before measuring.
- Watch too loose or tight: The watch should be snug on your wrist, not too loose or too tight.
- Talking or holding your breath: Breathe normally and don’t talk.
Golden tip: Always take the ECG in the same position and at the same time of day. That way your results are comparable and you detect real changes, not variations from how you were sitting.
What to do with the results
If it says “sinus rhythm”
Your heart beats with regular rhythm. That’s the normal result. You don’t need to do anything, but save it as a reference.
If it says “atrial fibrillation”
Don’t panic, but act:
- Save the recording (the watch does this automatically).
- Repeat the measurement after a few minutes.
- Consult your doctor and show them the recordings.
- AFib detected by smartwatch isn’t a diagnosis: it’s an alert for a professional to examine you.
If it says “inconclusive reading”
Repeat the measurement following the recommendations above. If it keeps failing, restart the watch and try again.
Real limitations of the smartwatch ECG
| What it CAN do | What it CANNOT do |
|---|---|
| Detect atrial fibrillation | Detect heart attacks |
| Confirm normal sinus rhythm | Detect heart blocks |
| Record and share with doctor | Replace a 12-lead ECG |
| Alert on abnormal heart rate | Diagnose heart diseases |
FAQ
Is the smartwatch ECG reliable?
Yes, for detecting atrial fibrillation it has 98% sensitivity according to clinical studies. It’s not a medical diagnosis, but it’s a very valid detection tool that can save lives.
How often should I take an ECG with my watch?
There’s no mandatory frequency. If you don’t have risk factors, once a month as a checkup is enough. If you have a history of heart problems, your doctor will tell you the frequency.
Does the ECG work if I have sinus tachycardia?
Yes, but the result may vary. The watch will warn you if it detects a high or low heart rate, but the basic ECG pattern will be visible.
Which smartwatch has the best ECG?
Apple Watch and Samsung Galaxy Watch are the most clinically validated. Both have FDA approval (US) and European regulatory approval. The accuracy difference between them is minimal.
Conclusion
How to use the smartwatch ECG correctly is simple if you follow the instructions: sit down, stay still, rest your arm, and keep the watch snug. The smartwatch ECG doesn’t replace a doctor, but it’s an early detection tool that can make a difference. Use it as a complement to your medical checkups, never as a replacement.