A Guide To Using Apple Watch and Kardia ECG devices-What They Can and Can't Do

Many patients (and perhaps physicians) are confused as to how best to utilize personal ECG devices. I received this question illustrating such confusion from a reader recently:

I first came across your website a year ago during persistent angina attacks, and returning now due to increasing episodes of symptoms akin to Afib. I bought a Kardia 2 yrs ago for the angina episodes, and looking to buy the Apple Series 4 for the Afib, as I want to try a wearable for more constant monitoring. What I would greatly appreciate if you had a basic guide for both the Kardia & Apple devices, specifically when and how to best employ them for unstable angina and detecting undiagnosed Afib. As in, what can I as a patient provide to you as a doctor for diagnosis in advance of a formal visit. I’m a US Iraq vet medically retired in the UK, and most of my concerns get dismissed out of hand as “anxiety”, not sure why they thought a stent would cure my anxiety though  

Personal, Wearable ECG Devices Won’t Diagnose Angina (or Heart Attacks)

First. please understand that none of these devices have any significant role in the management of angina. Angina, which is chest/arm/jaw discomfort due to a poor blood supply to the heart muscle cannot be reliably diagnosed by the single lead ECG recording provided by the Apple Watch, the Kardia Band or the Kardia mobile ECG device. Even a medical-grade 12 lead ECG doesn’t reliably diagnose angina and we rely on a constellation of factors from the patient’s history to advanced testing to determine how best to manage and diagnose angina.

Second, as you are having episodes “akin to Afib”, all of these devices can be helpful in determining what your cardiac rhythm is at the time of the episodes if they last long enough for you to make an ECG recording.

The single lead ECG recording you can make from the Apple Watch, the Kardia Band and from the Kardia mobile device can very reliably tell us what the cardiac rhythm was when you were feeling symptoms.

The algorithms of these devices do a good job of determining if the rhythm Is atrial fibrillation. Also, if the rhythm is totally normal they are good at determining normality.

However, sometimes extra or premature beats confuse the algorithms resulting in an unclassified tracing and (rarely) an inaccurate declaration of afib

These tracings can be reviewed by a competent cardiologist to sort out what the rhythm really is.

In all of these cases, having an actual recording of the cardiac rhythm at the time of symptoms is immensely helpful to your doctor or cardiologist in determining what is causing your problems.

My recommendation, therefore, would be to make several recordings at the time of your symptoms. Print them out and carefully label the print-out with exactly what you were feeling when it was recorded and present these to the doctor who will be reviewing your case.

As I’ve mentioned in previous posts (see here), my patients’ use of Kardia with the KardiaPro online service has in many cases taken the place of expensive and inconvenient long term monitoring devices.

Case Example-Diagnosing Rare And Brief Attacks Of Atrial Fibrillation

I recently saw a patient who I think perfectly demonstrates how useful these devices can be for clarifying what is causing intermittent episodes of palpitations-irregular, pounding, or racing heart beats.

She was lying on a sofa one day when she suddenly noted her heart “pumping fast” and with irregularity. The symptoms last for about an hour. She had noticed this occurred about once a year occurring out of the blue.

Her PCP ordered a long term monitor, a stress test and an echocardiogram.

The monitor showed some brief episodes of what I would term atrial tachycardia but not atrial fibrillation but the patient did not experience one of her once per year hour long episodes of racing heart during the recording. Thus, we had not yet solved the mystery of the prolonged bouts of racing heart.

She was referred to me for evaluation and I recommended she purchase an Alivecor device and sign up for the KardiaPro service which allows me to view all of her recordings online. The combination of the device plus one year of the KardiaPro service costs $120.

She purchased the device and made some occasional recordings when she felt fine and we documented that these were identified as normal by Kardia. For months nothing else happened.

Then one day in April she had her typical prolonged symptom of a racing heart and she made the recording below (She was actually away from home but had the Kardia device with her.)

When she called the office I logged into my KardiaPro account and pulled up her recordings and lo and behold the Kardia device was correct and she was in atrial fibrillation at a rate of 113 BPM.

With the puzzle of her palpitations solved we could now address proper treatment.

Continuous Monitoring for Abnormal Rhythms

Finally, let’s discuss the wearables ability to serve as a monitor and alert a patient when they are in an abnormal rhythm but free of any symptoms.

My reader’s intent was to acquire a device for “constant monitoring”:

I’m looking to buy the Apple Series 4 for the Afib, as I want to try a wearable for more constant monitoring.

This capability is theoretically available with Apple Watch 4’s ECG and with the Kardia Band (using SmartRhythm) which works with Apple Watch Series 1-3.

However, I have not been impressed with Apple Watch’s accuracy in this area (see here and here) and would not at this point rely solely on any device to reliably alert patients to silent or asymptomatic atrial fibrillation.

In theory, all wearables that track heart rate and alert the wearer if the resting heart rates goes above 100 BPM have the capability of detecting atrial fibrillation. If you receive an alert of high HR from a non ECG-capable wearable you can then record an ECG with the Kardia mobile ECG to see if it really is atrial fibrillation.

At 99$, the Kardia is the most cost-effective way of confirming atrial fibrillation for consumers.

I hope this post adds some clarity to the often confusing field of personal and wearable ECG devices.

Electroanatomically Yours,



4 thoughts on “A Guide To Using Apple Watch and Kardia ECG devices-What They Can and Can't Do”

  1. I just want to record: another superb well pitched review. This really is an excellent blog for the interested but non-medical reader.

  2. Other types of heart monitors include:
    Holter Monitor – for up to two weeks
    Implantable loop recorder – for up to three years
    Interested persons can Google these devices.

  3. An excellent and thorough response as always. When the best guess diagnosis is possibly unstable angina, and just given more statins, you grasp for straws. The Kardia Mobile at least empowered me to have something tangible to record anything that might supplement an oral account of an episode, and avoided many trips to the ER in the absence of worsening symptoms. On a few visits, they’ve observed early re-polarization, for what it’s worth. Plus, there are no side effects from excessive contact with the Kardia. When my frequency of angina attacks were outpaced fourfold with palpitations over the past year, not once has a provider suggested AFib, and I only became aware of AFib recently when I was trying to understand why I was having to lay down after these episodes because of the sudden fatigue 3-4 times daily. I’ve had some interesting ECG traces on my phone when I’ve managed to use my Kardia in time, but the palpitations can come and go so quickly. My primary goal is to have an easier and quicker way to take more frequent measurements, and ideally be alerted if something more significant is occurring. As I’ve received a number of referrals for non-military providers (UK), my out-of-pocket expenses for a single visit would easily pay for both a used iPhone and Apple watch. If the visit was for anything than yet another 12-lead ECG with a consult, I might comply, but I’d rather have a collection of readings over a period of time to present at my next appointment as opposed to these snapshot in time visits to the ER, or when I’m not symptomatic. Haven’t yet figured out how to make an appointment that will coincide down to the minute of experiencing symptoms! Thanks again for your time and consideration.

  4. I have an AW4 fitted with the Kardia Band. Recently on a ski trip both Kardia and Apple reported an abnormal rhythm, advising me to seek professional help.
    I sent the Kardia tracings to their board certified cardiologist reporting service, and PAC and PVB diagnosed.
    The Vail cardiologist ordered a 12 lead ECG which confirmed the diagnosis. My medication was adjusted.
    Back home, at the gym, I work out with the Kardia Smart Rhythm running. I received an alert, and noted my heart rate had jumped. Felt quite lightheaded during this episode.
    As I attend a geriatric gym, a 12 lead ECG was promptly taken, and confirmed PAC and PVB, and fortunately the gerontologist Professor was in attendance that day, so expert advice without delay.
    A low dose beta blocker was added, which has thus far stopped any further episodes.
    Kardia is owned by Omron, and when I upgraded my BP monitor to a Bluetooth enabled model, I had a few glitches because the move to a soft cuff from the hard cuff of the previous model meant a change in technique.
    When you sign up with Omron you give the rights to your data.
    The helpful Omron rep also explained that if the pulse wave has irregularities, as in PACs and PVBs, then the heart wiggle icon appears on the BP monitor screen, and that a reading with the heart wiggle icon is unreliable, and should be repeated.
    I sometimes get this heart wiggle icon, which I now know is a message that my heart rhythm is not regular, according to the Omron BP monitor.
    The Omron guy also explained that the optical system used for heart rate monitoring as in all the wrist heart rate monitors is also prone to this type of error.
    Chest strap monitors like the Polar H10 are electrical in nature, so are more accurate.
    Both the Kardia and Apple ECG systems have electrodes and are electric in operation, but the heart rate monitoring is optical.
    So I have retrieved my old H10, replaced the battery, and now use it connected to my iPhone for better heart monitoring during gym. I use the Polar app for this.
    The original KardiaMobile, a two pad attachment which I glued onto the case of my iPhone 4, has now been upgraded.
    To quote the message on my iPhone Max, the upgraded model has recently received FDA clearance for two new indications, tachycardia and bradycardia.
    This extra facility will soon be added to the Kardia band.
    In my experience both Kardia and Apple are very helpful, and the ability to get an expert report with Kardia makes it a very clear winner, along with your own cardiologist’s involvement.
    What gets measured gets managed.


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