What is the one heart condition a smartwatch can detect?

Last fall Apple introduced the Series 4 Watch with a built-in single-lead electrocardiogram (EKG). When they announced the watch, they also said they received FDA clearance for the EKG function.

What does this mean?

Apple was not the first company to make an over-the-counter EKG available. Alivecor received FDA clearance in 2014 with a smartphone case that had built-in leads.

In some ways it is quite amazing that individuals can easily get an EKG from a consumer electronic device.

But many physicians are not that impressed. The main reason why is that a single lead EKG can really only detect one type of heart condition reliably: atrial fibrillation (or AFib).

What is atrial fibrillation?

Our heart has four chambers: two atria and two ventricles. The right side receives blood from our entire body in the right atrium and pushes it to the right ventricle. The right ventricle then pumps this blood to our lungs to remove carbon dioxide and pick up oxygen.

The left side receives the oxygenated blood from our lungs in the left atrium, pushes it to the left ventricle which then pumps this blood to the rest of our body. So, you can think of the atria on both sides as the priming chambers, and the ventricles as the pumps.

In order for each chamber to pump blood, it must receive a firing signal. The atria have a built-in pacemaker that sends this signal and gives us our heart rate. But sometimes this pacemaker doesn’t work properly which is what happens in atrial fibrillation.

In this case, the individual groups of cells in the atria fire whenever they are ready to fire. This means there is no coordinated push from the walls of the atrial chamber to get blood into the ventricles.

Sometimes enough blood gets to the ventricles to pump to the lungs and the rest of the body, even without this coordination. And because the ventricles have their own built-in pacemaker to fire with coordination, some people with atrial fibrillation feel fine.

However, in some cases, not enough blood gets to the ventricles to pump out to the lungs and the rest of the body. These people may feel dizzy, tired or weak, or if they already have heart disease, they may have chest pain.

If atrial fibrillation continues for a long period of time, a little bit of blood can just sit in the atria and form clots. This usually happens in a part of the atria call the appendages.

The problem with clots forming in the heart is that they can eventually break loose and go to the lungs or the rest of the body. Two really bad things can happen as a result: pulmonary embolism or stroke.

Pulmonary embolisms are bad because they keep blood from getting to parts of your lungs. And the clot forming the embolism is big enough, it can back up blood to the heart and cause death. The clots formed in atrial fibrillation are usually small, and when they cause pulmonary embolisms, people may not even notice.

(A more common cause of pulmonary embolisms is deep vein thrombosis, usually formed in the legs. These clots tend to be bigger and are more dangerous.)

If clots from the left atrium break off and go to the rest of the body, the first place they are likely to go is to the brain. Even small clots in the arteries that feed the brain can cut off its blood supply. The brain can only function for a few minutes without oxygen from blood, so the parts of the brain that don’t receive blood are damaged, resulting in a stroke.

If the symptoms of a stroke or pulmonary embolism are recognized quickly, getting that person to the emergency room is the best thing to do. If the symptoms started within three hours, doctors can give clot-busting medication to restore blood flow and possibly reverse any damage that occurred. (For stroke, think F.A.S.T: Face drooping, Arm weakness, Speech difficulty – Time to call 9-1-1!)

Why should I care?

The big picture

We don’t know exactly how many people develop atrial fibrillation on a short-term basis (acute), so having these EKGs available to consumers may shed more light on this. We know more about the number of people that develop atrial fibrillation on a long-term basis (chronic), probably because they develop symptoms that lead to their diagnosis.

Overall, chronic atrial fibrillation is common, but not really common (which also might be why many physicians are jumping up and down with excitement).

Now that there are devices like these available to consumers, expect to see more of them. And there are already otoscopes and multi-function devices to enable virtual visits with physician.

For you personally

If you have a family history of atrial fibrillation, these devices may help you keep an eye on how your heart is doing.

Also, there are numerous reports of plain old heart rate monitors (without the EKG function) helping people learn that they have a high heart rate for long periods of time, even when they weren’t exercising. This led them to get evaluated by a doctor and diagnosed with other types of heart arrhythmias. (In fact, one of our friends had this very thing happen.)

Where to find more information

In full disclosure, my husband works for Apple. However, I my goal here is to help you understand more about atrial fibrillation and what you can do about it.

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