What Sinus Arrhythmia Looks Like on Your Watch ECG

Sinus Arrhythmia: Is it a Cause for Concern?

Key Takeaways

  • Most cases of respiratory-linked sinus arrhythmia are normal and indicative of a healthy heart.
  • Smartwatch ECGs like the Apple Watch, Fitbit, and Samsung Watch can help you monitor your heart for sinus arrhythmia and other heart rhythm abnormalities.

Sinus arrhythmia means an abnormality in the heart rhythm and that the heart is beating irregularly. Usually, the heart beats at a regular pace like a clock. The time interval on an ECG tracing between each heartbeat is called the R - R wave interval. During sinus arrhythmia, the variation in the R-R interval is greater than 0.12 seconds.1

Sinus Arrhythmia recorded by an Apple Watch ECG
Sinus Arrhythmia recorded by an Apple Watch ECG

Sometimes the heart rate changes when you breathe in and out, known as respiratory sinus arrhythmia. It is common in young people and is usually harmless. However, another form of sinus arrhythmia is not affected by breathing. Instead, the heart beats irregularly, and there is a lengthened R-R interval on an ECG tracing. Sometimes this is transient, but it can also be due to underlying heart disease.

Sinus Arrhythmia recorded by Apple Watch, reviewed by QALY
Sinus Arrhythmia recorded by Apple Watch, reviewed by QALY

Common Symptoms of Sinus Arrhythmia

Most cases of sinus arrhythmia do not cause any symptoms, so unless you were looking at a heart monitor or smartwatch, you would not know you had a problem. However, some people can experience lightheadedness due to the slowed heart rate, particularly in non-respiratory sinus arrhythmia.

Any Cause for Concern?

Most cases of respiratory-linked sinus arrhythmia are not dangerous. In fact, most sinus arrhythmia cases are normal and indicative of a healthy heart. The irregular beating from the sinus node (which causes sinus arrhythmia) can be a normal finding in young, otherwise healthy individuals. However, there can be a lot of fluctuation of the heartbeat that may vary with normal breathing in some people. So, if sinus arrhythmia is a concern for you, know that most cases are normal findings.

However, sometimes the recording detects movement and interference known as artifacts, which can appear as abnormal on a trace. The important thing is to consider how you are feeling. For example, if you feel dizzy or lightheaded, experience breathlessness, or have chest pain, you should see a doctor immediately. As a layperson who is not used to reading ECG tracings, it is hard to assess whether your irregular trace is a problem or not. Thankfully, you can access a service like QALY, where an expert will tell you what the tracing shows, such as a normal sinus arrhythmia tracing.

How a Smartwatch ECG Can Capture Arrhythmias

Smartwatches like the Apple Watch, Fitbit, and Samsung Watch have a lot of features that you will find helpful. They monitor the level of exercise you do and can calculate calories burned. Many smartwatch designs also feature an ECG recorder. They are easy to set and record your heart rhythm. People use the features to monitor general fitness, but sometimes the watches can be used to record symptoms in people who have experienced problems such as palpitations or dizziness. A smartwatch uses a green LED light and photosensors on the back of the watch to monitor blood flow in the capillary veins and detects the heart rhythm.

The ECG recorder on a smartwatch does not record a full 12-lead ECG to look at all the different areas of the heart that you would get if you visited a doctor. Instead, you simply get a single lead tracing with a smartwatch. You can also get a heart tracing from small portable devices such as KardiaMobile from AliveCor and from some home blood pressure monitoring kits.

Example of Sinus Arrhytmia cought with smartwatch
Example of Sinus Arrhytmia cought with smartwatch

When Should You Seek Advice from a Doctor?

If you think there is an irregular heart rhythm on your smartwatch ECG and also feel unwell, such as feeling dizzy, breathless, or have chest pain, you should call a doctor or 911. But what if you are unsure about the tracing or notice a change, you can submit your ECG to the QALY app, where a clinical expert can check your smartwatch tracing and advise you on what to do next. There won't be a problem most of the time, but occasionally you may need to see a doctor for a sinus arrhythmia ECG problem.

Still Not Sure How to Spot Sinus Arrhythmia?

One of the benefits of a smartwatch is that you have many features to help you stay healthy. Aside from looking at heart tracings, take time to use some of the other apps to learn how the watch works with calorie counting, healthy exercise, and sleep patterns. All these help you to have a healthy lifestyle and protect your heart. Learning to use your smartwatch features will enable you to make the best use of the device, and the more you utilize the apps, the more you will benefit from the various gadgets.

Finally, if you are concerned about the ECG tracings from your smartwatch, you can get them reviewed by experts for arrhythmias within minutes on the QALY app. It will give you peace of mind and help you to get an assessment if needed. So reach out to us if you have any questions.


1. Soos, M and McComb, D. Sinus Arrhythmia. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK537011/

Get second opinions of your ECGs on the QALY app!

Get second opinions of your ECGs on the QALY app!

Not Sure If It's Sinus Arrhythmia? Get Your ECG Analyzed by Experts on the QALY App.

Interpret My ECG Now

By using this website, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. View our Privacy Policy for more information.