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Disclaimer: Due to health regulations and clearances, some ScanWatch features may not be available or may not have clinical validation in your region. Learn more.

What is an ECG?

ECG, or electrocardiogram, is the graphical representation of the electrical activity of the heart. It can detect certain cardiovascular pathologies.

With each heartbeat, an electrical wave travels through your heart. This wave causes your heart to contract and pump blood.

The gold standard ECG records 12 lead (or ways) of the heart. Withings ECG devices sense the electrical activity of the heart at a distance through the left and right arm. This configuration is known as lead D1.


What practitioners look for in the ECG graph?

A normal heartbeat on the ECG graph will show the time the electric wave takes to move through your heart. There are 3 distinct patterns:

First wave: The "P wave"

The graph shows a first electric wave as electricity moves into the right and left upper chambers of your heart.


Next wave: the "QRS Complex"

This second pattern shows electricity moving through the right and left bottom ventricles.


 Final wave: the "T wave"

The final wave represents electrical recovery or returns to a resting state for the ventricles.


By measuring time intervals on an ECG, practitioners can find out if this electricity travel is too slow, normal, too fast, or even irregular. Such indicators can point to an oversized or overworked heart.

Which conditions can detect Withings ECG devices?

ECGs can detect a range of conditions, from angina pectoris to severe heart attacks. Withings ECG devices focus on detecting atrial fibrillation. If you believe you are having a heart attack, contact emergency services.

Results you may see

Normal Sinus Rhythm 

A sinus rhythm means your heart is beating in a uniform pattern.


Atrial Fibrillation 

Atrial fibrillation occurs when the two upper chambers of the heart move chaotically instead of pumping regularly. The P wave on the ECG disappears and is replaced by a jumpy baseline. The QRS complex occurs at "irregularly irregular" intervals. 



An inconclusive result means the recording can’t be classified. This can happen for many reasons: 

  • Heart rate is low: The heart rate obtained cannot be classified as a recording. To obtain full analysis, the heart rate must be above 50 bpm during the recording.
  • Heart rate is high: The recording does not appear to show any signs of atrial fibrillation, but a complete diagnosis is not possible for a heart rate above 100 bpm. To obtain full analysis, the heart rate must be below 100 bpm during the recording.
  • Signal is too noisy: There is too much interference for the recording to be classified. Place your arm on a table or on your thigh, relax, don’t talk, and don’t move during the recording. Refer to the best practices section to know the right gestures to be adopted and those to be avoided.
  • Signs of other arrhythmia: This sensor is capable of detecting atrial fibrillation, but is not able to diagnose other types of arrhythmias. This recording cannot be classified as normal rhythm or atrial fibrillation.

Note that atrial fibrillation can be episodic rather than continuous. This can cause the algorithm used by ScanWatch to fail for some types of arrhythmia other than atrial fibrillation, particularly in the case of extrasystole (a premature beat of one of the heart's chambers which leads to momentary arrhythmia). With the ScanWatch's medical-grade graph, a cardiologist can provide you with a more accurate diagnosis.

If you receive an undefined result due to a poor recording, you might try to re-record your ECG. Click here for more information.

If you encounter issues with your ECG recordings, click here.

Important: If you think you may be having a heart attack (myocardial infarction) or are facing a medical emergency, call the emergency services.

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