Can a Smartwatch detect a Heart Attack or Cardiac Arrest

Can a Smartwatch detect a Heart Attack? No. I am no doctor or professional in this topic, but based on my research on the topic there is no smartwatch out there that could detect a heart attack. A heart attack is blood “circulation” problem and can’t be diagnosed based on heart rate alone. Diagnosis is usually based on symptoms, ECG results, and blood tests.

What about a Cardiac Arrest, can Smartwatches detect those? Not really, but let’s say it can be helpful. Again I’m no expert and my answer is based on my research on the topic. Cardiac Arrest is when the heart stops beating suddenly. So yes the smartwatch could detect no pulse but how would it know if the sensor is just not having a good contact versus the heart-stopping? The smartwatch could also detect a fall after the person loses consciousness. In any case, it’s most likely too late if no one is nearby witnessing the event and being able to provide immediate assistance.

However, smartwatches do collect heart rate data which can be used to detect abnormal heart rhythms via Artificial Intelligence. Even if this doesn’t pinpoint a specific heart-related disease this proactive approach of notifying users might be able to prevent future issues if the user sees a doctor and problems are detected early.

Heart Attack versus Cardiac Arrest

People often use these terms interchangeably, but they are not the same. A heart attack is when blood flow to the heart is blocked, and sudden cardiac arrest is when the heart malfunctions and suddenly stops beating unexpectedly. A heart attack is a “circulation” problem and sudden cardiac arrest is an “electrical” problem.

These two heart conditions are linked though. Sudden cardiac arrest can occur after a heart attack, or during recovery.  Heart attacks increase the risk for sudden cardiac arrest. Most heart attacks do not lead to sudden cardiac arrest. But when sudden cardiac arrest occurs, a heart attack is a common cause.

What is a Heart Attack

A heart attack (myocardial infarction or MI) is a serious medical emergency in which the supply of blood to the heart is suddenly blocked, usually by a blood clot. A lack of blood to the heart may seriously damage the heart muscle and can be life-threatening.

This is a summary of the information provided by NHS – National Health Service in the UK.

Symptoms of a heart attack can include:

  • chest pain – the chest can feel like it’s being pressed or squeezed by a heavy object, and pain can radiate from the chest to the jaw, neck, arms and back
  • shortness of breath
  • feeling weak and/or lightheaded
  • overwhelming feeling of anxiety

It’s important to stress that not everyone experiences severe chest pain; the pain can often be mild and mistaken for indigestion.

It’s the combination of symptoms that’s important in determining whether a person is having a heart attack, and not the severity of chest pain.

What is a Cardiac Arrest

Sudden cardiac arrest occurs suddenly and it is triggered by an electrical malfunction in the heart that causes an irregular heartbeat (arrhythmia). With its pumping action disrupted, the heart cannot pump blood to the brain, lungs and other organs. Seconds later, a person loses consciousness and has no pulse. Death occurs within minutes if the victim does not receive treatment.

Each year in the United States, more than 350,000 cardiac arrests occur outside of a hospital setting.

What is a Stroke

A stroke occurs when blood, which carries oxygen to the brain, is blocked. It is a medical emergency because brain cells begin to die within a few minutes without oxygen. Ischemic strokes account for 87 percent of all strokes. They happen when there’s a blood clot that blocks blood flow to a part of the brain.

How Smartwatches could predict Heart Problems

A new study published in the Journal of the American Medical Association (JAMA) suggests that life-saving heart monitoring can be performed with just about any heart-rate-enabled smartwatch and the Cardiogram Android app. It might not be able to pinpoint a specific disease but instead, it might be able t accurately detect specific types of abnormal heart rhythms.

Surprisingly, the 97-percent accuracy measured by the study is a higher rating than that attainable with the Apple Watch’s FDA-cleared ECG accessory.

Apple Watch’s ECG feature is FDA-cleared to detect atrial fibrillation (an irregular heart rate that increases your risk for stroke and heart failure) and to give users notifications that their heartbeat is irregular. The watch also notes when a person’s heart rate is too low.

iBeat Heart Watch

There are multiple articles about the iBeat Heart Watch being able to detect Cardiac Arrests and summoning help. None of the articles or the iBeat website explain how does it actually detect a Cardiac Arrest. The iBeat website says that optical sensors track your heart’s every beat. If your heart slows or stops, they will immediately alert you and their response team. Based on the heart rate disappearing there really isn’t any way of knowing is the sensor having a poor connection or did the heart actually stop. The watch will ask you “Are you okay?” if it detects an issue. Well, I guess you would be unable to respond if you lost consciousness, but if there isn’t anybody around witnessing the event would anyone make it in time?

The device is advertised as being a sleek, stylish smartwatch that monitors your heart for unsafe parameters. In an emergency, they say they will alert you, your loved ones, and their dispatch team to get you immediate care and potentially save your life.

The device has strong claims but no clinical studies to back them up. I think Smartwatches can provide great benefits and possibly save lives in preventive care and that’s where we will see the first advances. Cardiogram has some really interesting progress with the preventive care part. However, for acute events like a Cardiac Arrest, I don’t think I would put my life in the hands of a smartwatch. There are however Implantable Cardioverter Defibrillators (ICDs) that can actually autonomously monitor your heart rate and give an electric shock to restore a normal heartbeat.


In the Cardiogram for Employers program Cardiogram is a free app available to employees on the Apple App Store and Google Play Store, enabling them to track their heart rate fluctuations using consumer wearables like Apple Watch, wearOS, and Garmin.

Cardiogram analyzes the data on its servers with DeepHeart, a clinically-proven artificial intelligence algorithm that uses heart rate and step count data to screen the employees for multiple major health conditions.

If the DeepHeart algorithm flags an employee with a condition, the employees will be requested to take an FDA-cleared diagnostic test.

What makes Cardiogram interesting is that they have undergone clinical testing in a series of N=14,011 studies with UC San Francisco’s cardiology department. Cardiogram also states that they provide a return on investment in the form of savings of $2,120-$7,301 per employee annually by reducing medical spend from future health complications, and reducing productivity losses from sick days.

Cardiogram outside the employer program

You can install and use the Cardiogram app without being included in an employer program. I installed the app from the Google Play Store on my android smartphone and connected it to Garmin Connect. With Garmin at least it actually doesn’t need a connection to the Smartwatch but instead, it connects to Garmin Connect on the server side. This makes a lot of sense since your smartwatch can just send the data to one place and Garmin can then via its API allow using the information to third parties if you give consent to it.

On the Google Play Store, the app description says that it allows you to share your health data with medical researchers, to contribute to studies on abnormal heart rhythms like atrial fibrillation, heart failure, and more. It also says that Cardiogram is not a medical device and is currently for research purposes only.

It’s unclear to me will my data be analyzed by DeepHeart and would I get any notifications of potential conditions outside the employer program.

Cardiogram in clinical studies

Consumer wearables like Garmin, Fitbit, and Apple Watch will generate far too many health measurements for any human doctor to review. To help create the future of preventive medicine, Cardiogram is building DeepHeart, a deep neural network tested in multiple clinical studies.

Cardiogram is working towards closing the diagnostic gap by using artificial intelligence to transform existing wearables into screening tools for diabetes, hypertension, sleep apnea, and atrial fibrillation.

Atrial Fibrillation is the most common abnormal heart rhythm. It causes 1 in 4 strokes and frequently goes undiagnosed. In the mRhythm Study, DeepHeart detected atrial fibrillation with 97% accuracy (c-statistic) using optical heart rate sensors, setting the stage for cost-effective, broadly-deployed AF screening.

A study (Passive Detection of Atrial Fibrillation Using a Commercially Available Smartwatch)  published in May 2018 in the Journal of the American Medical Association (JAMA) suggests that commercially available smartwatches coupled with a deep neural network classifier can passively detect atrial fibrillation.

Atrial fibrillation (AF) affects 34 million people worldwide and is a leading cause of stroke. So a means to continuously monitor for AF could prevent large numbers of strokes and death.

Advancements like this which are backed up by studies make me very optimistic that smartwatches and wearables, in general, will be an essential part of our everyday lives in the future. It might be that your health insurance policy gives you a discount if you wear a device and participate in preventive care programs.

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Hi! I'm John and this is where I share my tech learnings. As a tech enthusiast and a smartwatch believer (I wear a Garmin smartwatch), I like to read about the newest trends and research new devices. On this blog, I share all the things I learn about smartwatches as I go.

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