Analyses & Studies

Focus Healthcare: How Accurate are Smartwatches at Detecting Irregular Heart Rhythms?

You may have heard of people with smartwatches that have alerted them of an irregular heart beat or may even have received alerts from your own smartwatch that your heart rhythm is irregular or perhaps too slow at night. Such alerts may cause added stress and anxiety but may also be potentially life-saving if there is really an underlying heart problem. With an increasing number of people wearing these devices, such alerts are becoming more common. But just how accurate are smart watches with ECG capability at detecting abnormal heart rhythms (cardiac arrhythmias) and when should one be concerned? Can smart watches really detect a silent heart condition, even before one develops symptoms? 

Atrial fibrillation (AFib)- an important cardiac arrhythmia detected by smartwatches 

It actually turns out that smartwatches with ECG capability are surprisingly accurate in detecting some types of arrhythmias, especially those causing irregular heartbeats, such as atrial fibrillation (AFib). AFib occurs when the heart rhythm becomes fast and irregular and the top chambers of the heart (called the atria) beat rapidly and faster than the lower chambers (called the ventricles). People with AFib may feel palpitations (the awareness of the heart beating fast or abnormally) or sudden breathlessness or dizziness. However, some people may not have any symptoms and AFib may be detected incidentally on their smart watches. AFib is more common in older people, especially those with other medical conditions such as high blood pressure and diabetes, but it can also sometimes occur in younger people with no pre-existing medical problems. Ironically, people who are very fit and engage in endurance sports such as long distance running and cycling, may be at increased risk of developing AFib due to the repeated stresses on their heart and stretching of their atria. The concern about AFib is that the condition increases the risk of blood clots developing in the heart (which can lead to a stroke) and can weaken the heart muscle if it is present for a long time and left untreated. 

Are smartwatches with ECG capability accurate at detecting AFib? 

The ECG technology in a smartwatch uses LEDs flashed against the skin to detect blood flow and measure the heart rate. Sensors collect the information and algorithms are used to interpret the heart rhythm. If the device detects an irregular rhythm, it sends the wearer an alert. On the whole, the latest smartwatch technology is actually quite accurate at detecting AFib. Several large medical studies, such as the Apple Heart Study and the Fibit Heart Study (both enrolled > 400,000 participants) confirmed the medical usefulness of these devices and a high rate in detecting AFib. Certain series of smartwatches with ECG capability are now FDA-approved to help uses identify signs of AFib. 

However, one should also be aware of the limitations of smartwatches in detecting abnormal heart rhythms. Movement artefact or poor contact can reduce the quality of the recordings and give rise to alerts when in fact the rhythm is normal. These are so called “false positive” alerts. Conversely, smartwatches may sometimes fail to detect an abnormal heart rhythm in cases where the arrhythmia is more regular or when the it occurs when the person is not wearing the device. 

When should you seek medical attention if you have an abnormal rhythm alert on your smartwatch? 

I recommend seeking further medical advice and proper evaluation in the following situations if you receive an abnormal rhythm alert on your smartwatch: 

  • If you have any symptoms such as palpitations, sudden dizziness or breathlessness. 

  • If you have any cardiac risk factors, such as high blood pressure, diabetes, high cholesterol levels or have a history of a heart problem such as coronary artery disease or weakened heart muscle. 

  • If your smartwatch appears to detect AFib on multiple occasions or consistently reports very slow heart rates (<40bpm at night or < 50bpm during the day) which is much lower than your usual resting heart rate. 

It should be noted though that wearing a smartwatch doesn’t take the place of healthy living. The best ways to reduce the chances of AFib developing are to stay active, avoid excessive alcohol and address any cardiac risk factors such as high blood pressure and diabetes. Sleep apnoea can also increase the risk of AFib so if you have any symptoms of sleep apnoea (such as loud snoring at night or excessive tiredness during the day) and alerts on your smartwatch of an irregular rhythm, you should seek medical attention. 

By Dr Reginald Liew, Senior Consultant Cardiologist, The Harley Street Heart & Vascular Centre 

SOURCE: The Harley Street, Heart & Vascular Centre

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