Putting The Apple Watch 4 ECG To The Test In Atrial Fibrillation: An Informal Comparison To Kardia

My first patient this morning, a delightful tech-savvy septagenarian with persistent atrial fibrillation told me she had been monitoring her rhythm for the last few days using her Apple Watch 4’s built in ECG device.
Previously she had been using what I consider the Gold Standard for personal ECG monitoring- AliveCor’s Kardia Mobile ECG   and I monitored her recordings through our Kardia Pro connection.
I had been eagerly awaiting Apple’s roll out since I purchased the AW4 in September (see here) and between patients this morning I down-loaded and installed the required iPhone and Watch upgrades and began making AW4 recordings.
Through the day I tried the AW4 and the Kardia on patients in my office.

Apple Watch 4 ECG Is Easy and Straightforward

The AW4 ECG recording process is very easy and straightforward. Upon opening the watch app you are prompted to open the health app on your iPhone to allow connection to the Watch ECG information. After this, to initiate a recording simply open the Watch ECG app and hold your finger on the crown.
Immediately a red ECG tracing begins along with a 30 second countdown.
Helpful advice to pass the time appears below the timer:
“Try Not to move your arms.”
“Apple Watch never checks for heart attacks.”
When finished you will see what I and my patient (who mostly stays in sinus rhythm with the aid of flecainide) saw-a declaration of normality:
Later in the day I had a few patients with permanent  atrial fibrillation put on my watch.
This seventy-something farmer from Bowling Green, Missouri was easily able to make a very good ECG recording with minimal instruction

The AW4 nailed the diagnosis as atrial fibrillation.
We also recorded a Kardia device ECG on him and with a little more instruction the device also diagnosed atrial fibrillation
After you’ve made an AW4 recording you can view the PDF of the ECG in the Health app on your iPhone where all of your ECGs are stored. The PDF can be exported to email (to your doctor) or other apps.

ECG of the Bowling Green farmer. I am not in afib.

Apple Watch Often “Inconclusive”

The AW4 could not diagnose another patient with permanent atrial fibrillation and judged the recording “inconclusive”
The Kardia device and algorithm despite a fairly noisy tracing was able to correctly diagnose atrial fibrillation in this same patient.
I put the AW4 on Sandy, our outstanding echo tech at Winghaven who is known to have a left bundle branch block but remains in normal rhythm and obtained this inconclusive report .

Kardia, on the other hand got the diagnosis correctly:

One Bizarre Tracing by the AW4

In another patient , an 87 year old lady with a totally normal recording by the Kardia device, the AW4 yielded a bizarre tracing which resembled ventricular tachycardia:
Despite adjustments to her finger position and watch position, I could not obtain a reasonble tracing with the AW4.
The Kardia tracing is fine, no artifact whatsoever.

What can we conclude after today’s adventures with the Apple Watch ECG?

This is an amazingly easy, convenient and straightforward method for recording a single channel ECG.
I love the idea that I can record an ECG whereverI am with minimal fuss. Since I wear my AW4 almost all the time I don’t have to think about bringing a device with me (although for a while I had the Kardia attached to iPhone case that ultimately became cumbersome.)
Based on my limited sample size today, however, the AW4 has a high rate of being uncertain about diagnoses. Only 2/3 cases of permanent atrial fibrillation were identified (compared to 3/3 for the Kardia) and only 4/6 cases of sinus rhythm were identified.
If those numbers hold up with larger numbers, the AW4 is inferior to the Kardia ECG device.
I’d rather see the AW4 declare inconclusive than to declare atrial fibrillation when it’s not present but this lack of certainty detracts from its value.
What caused the bizarre artifact and inconclusive AW4 tracing in my patient is unclear. If anybody has an answer, let me know.
We definitely need more data and more studies on the overall sensitivity and specificity of the AW4 and hopefully these will be rapidly forthcoming.
For most of my patients the advantages of the AW4 (assuming they don’t already have one) will be outweighed by its much greater cost and we will continue to primarily utilize the Kardia device which will also allow me to view all of their recordings instantaneously in the cloud.
Conclusively Yours,
Note. The original version of this post had the wrong ECG tracing for the first “inconclusive” AW4 recording of a patient with permanent atrial fibrillation. H/t to discerning reader Vignesh for pointing this out months after the initial posting.


13 thoughts on “Putting The Apple Watch 4 ECG To The Test In Atrial Fibrillation: An Informal Comparison To Kardia”

  1. The extremely noisy reading can be caused by sweat or other humidity. If the electrode on the bottom of the Watch and/or the finger with which is you touch the crown electrode is damp/wet – it’ll produce extremely erratic readings. Try making an ECG after a shower, it’ll be noisier than the average death metal band.

  2. The Kardia watch band had a handy program called Smart Rhythm. Unfortunately, this has been discontinued. Kardia Support advise that this was due to changes Apple made that meant that their program became incompatible.
    I found Smart Rhythm handy while working out at gym. Once it picked up an issue, which was confirmed PACs and PVBs by the 12 lead EKG performed by the gerontologist, who luckily was at the gym that day.
    Now that Smart Rhythm has been discontinued, do you have any suggestions for an app that continuously monitors heart rhythm and alerts for possible irregularities?
    I have AW4 but prefer the Kardia Watch band over the Apple EKG. I am not familiar with any of the AW4 Apps, so would appreciate your advice.

  3. Hi
    Thanks for the post. I have a question. You have mentioned that the AW4 device reports inconclusive ECG for one recording with AFib and one with normal rhythm. But on closer inspection, the AW4 ECG recordings you have uploaded for both the cases appear almost identical. Are you sure you have upload the respective files for each case? Kindly clarify.

    • Vignesh,
      You are correct! Thanks so much for pointing this out. You are the first of several thousand readers to notice this. I have retrieved the correct tracing for the patient with permanent atrial fibrillation and it is now in the post replacing the duplicate. It obviously shows atrial fibrillation whereas the original image did not.

  4. I do not have Afib, nor have I ever used the Kardia.
    However, I was diagnosed with a 98% blockage in my widowmaker and decided to refuse stents or bypass and instead shift to a no oil plant based diet supplemented with the Pauling Rath Protocol, which for my level of blockage is 3 g Vitamin C + 3 g L-Lysine + 3 g L-Proline and 25 mg Niacin (this is adjusted over time to make sure you get the Niacin Flush), also bought a puppy and started walking.
    Sept 3rd ’18 Angiogram clearly showed the blockage with two others at about 50% and ultrasound measurement of LVEF was 17%.
    Feb 13 ’19 My LVEF was measured again and was 52% with my cardiologist commenting that my heart was clearly beating much more. (We are going to find out in two weeks with a 2nd Nuclear Perfusion Stress ECG if the muscle is dead or hibernating. It appears if a good deal was in the hibernation state, which I never knew your heart could do.)
    My daughter bought me the Apple Watch 4 because of the obvious risk of heart attack.
    In my ECGs 9-10-17, my ECGs were normal and I had no chest pain and was eating mainly a Paleo diet. (No stress test but I had No Symptoms)
    One feature of my ECGs taken since 9-3-18 was a negative T wave and no P wave.
    5 months into this diet exercise program, my watch is starting to show a small positive T & P wave, which were confirmed in my last 12 lead ECG at the hospital.
    I think like anything new, as more refining is done the software will improve.
    I have been using Apple Computers since 1989. I only once upgraded a System at 7.0 and regretted it until 7.2!
    I use the ECG and the Workout App. I do High Intensity Training (I dance wildly to music until out of breath. The peak heart rate and recovery only works about one time in 5 which Apple states quite clearly can happen in this particular setting (I find that odd because the Heart monitor is clearly showing it reading my heart beat, but that program says it cannot make a graph). I am sure as more data comes in and Apple sees how many cardiac patients are using this, it will improve.
    Was Kardia 1.0 perfect? Has it been tweaked and upgraded?
    As to your question about the jumpy lines, I find I need to turn the band so the watch is on my inner wrist (thinner skin? Less sunlight-tan gives better reading? Any African-South India origin using this?) and locked down tight, I get a better reading.
    On the outside of my wrist even tight there is a jumpiness each time I breathe in. Does that woman have any tremors?
    Own 5 Apple computers, 2 iPhones, 2 watches, and a dead iPad. I do not own any Apple stock and given how many computers of theirs I have been responsible for people buying, Apple should send me a check! I am sure it must be in the mail. LOL
    I would look at Cleveland Clinic’s Dr. Esselstyn’s book on reversing heart disease using diet. Then add the Pauling Rath Protocol.
    Hope this is useful.

  5. After six weeks of use I am quite satisfied with the change to my apple 4 from my Kardia band. As I indicated before, my biggest problem with the Kardia was my frequent PACs confused the readings giving me false afib readings or frequent unclassified readings. In the six weeks I have had no confusion on the Apple 4. The only time it has given me a reading that did not read normal was earlier this past week when I had a short period of aflutter, where it alerted me that my heart rate was abnormally high. I checked my Kardia device, which I still carry with my iphone and it read unclassified and finally possible Afib. Many times in the past month when I knew I was having PACs I used both and always had a normal reading on the apple watch and either unclassified or possible afib on the kardia. My conclusion is that the apple watch is superior for my purpose as it seems to not be confused by my PACs.
    I am interested in others experience as more use both.

    • I have had similar experience with PACS and Kardia.
      In addition both Qardia and Omron had wiggly heart icons that turned out to be PACS.
      So AW4 showed normal sinus, while the Kardia, Omron and Qardia reported a possible problem.
      Send Kardia for specialist report and PACS diagnosed, but subsequent 12 lead specialist EKG gave normal sinus rhythm.
      While some advise that PACS can be ignored, I choose to try some lifestyle management- training sessions a little longer so HR not so close to Max, fewer HIT sessions, and to cut back on alcohol and chocolate. Seems to be helping in that all 4 devices now report no irregularities.

      • I am curious about others experience. If I were to believe my Kardia I am in “possible Afib” almost daily. I check my Apple Watch 4 and it shows my irratic pattern with pacs but says NSR. I generally know when I am in Afib, and I absolutely recall the PACs that precede my Afib and Aflutter by since I have been on Tikosyn it no longer goes there, thank heaven. It generally calms quickly and both Kardia and Apple Watch then read Normal sinus rhythm. I am surprised that the skeptical cardiologist feels the Kardia is superior. I am sure we are all different but I am curious to know if others share our experience.

  6. The important advantage of the Kardia band (also the original two pad mobile) over the AW4 is the rapid expert reporting on any ECG that shows an irregularity. And the ability of cardiologists like Dr P to access and review remotely.
    The Kardia review costs are modest, with the choice of a technician report at very reasonable cost, or a cardiologist report at a slightly higher cost. Reports delivered very promptly in my limited experience.
    Interestingly, the Qardioarm BP monitor identified cardiac irregularities while the Kardia Smart Rhythm on AW3 gave no alerts, despite some yellow lines on graph. Perhaps a fit 73 year old skiing at 11,000 feet defeated their algorithm.
    Would recommend Qardioarm despite a few quirks, and am perplexed by Apple’s outrageously stupid claims about AW4 being first ECG. Trust is difficult to build, and easy to damage. I now have doubts about the probity of Apple.
    Perhaps recent fall in price of Apple stock reflects these doubts. Deja vu all over again when the marketeers run a tech company.
    Thanks Dr P – your posts much appreciated.

  7. Feedback on Apple Watch Kardia Smart Rhythm app would be appreciated. Especially in comparison to the Apple Watch 4 Heart app.
    When Kardia Smart Rhythm is running on my Apple Watch 3 the movement monitoring functions are shut down.
    So the watch is now dedicated to solely monitoring heart rhythm.
    It seems to me that notifications via the Smart Rhythm app are more accurate than the native Apple Heart app, but I think that with the Apple app the activity monitoring is unaffected.
    I have the Kardia Bluetooth device attached to my iphone, but will soon get a Kardia band for the watch.
    Thanks for these posts – very interesting and much appreciated.

  8. This and your prior comments about the Kardia product and Apple watch seem consistent with the possibility that you are a paid “consultant” to AliveCor. Although I appreciate your experience, if you have any ties to the Kardia product this should be revealed, and if not, please state so.
    JCM, MD

    • Dr. Moore,
      I’m glad you brought this up.
      My previous post about Kardia Pro was very positive but if you look at all I’ve written about Kardia and AliveCor over the last 5 years you will see it is very balanced and often points out inaccuracies of the device. Because my post on KardiaPro eliminating need for long term monitors was so positive I posted the following at the end of it.
      N.B. I realize this post appears to be an unmitigated enthusiastic endorsement of a commercial product which is quite uncharacteristic for the skeptical cardiologist.
      One might wonder if the skepcard is somehow biased or compensated for his endorsement of Kardia.
      In all honesty, this sprung from my love of the device’s improvement in my afib management and I have received no payment, monetary or otherwise from AliveCor and I own none of their stock (and I’m not even sure if it is on the stock market.)
      This statement is still true and I still don’t know if Alivecor is listed on the stock market.

  9. Interesting. I have been using the Kardia band on my apple 3 watch for a year and paid for the premium plan as well. I ordered the new Apple Watch 4 today, since the app is finally out. I found the Kardia very helpful until I began Tikosyn. I have frequent PACs which seems to confuse the reading now, as my EP tells me I am in normal rhythm, and While I often don’t feel normal, I can tell the difference, but Kardia says possible afib or unclassified.
    I am grateful for the Kardia till now….not one useless hospital ER, despite some rough months. Between Kardia,my doctor, and my own calm monitoring I knew when I was NOT in trouble.
    I had hoped the apple watch4 would be better but your testing is discouraging. However, with trade in on my A watch3, and the cancellation of my monthly $9.99 charge for the Kardia Premium, I feel it will not really be more expensive. (And my vanity has finally been served. i can go back to stylish watch bands. ?‍♀️) My pleas to Kardia went unnoticed.
    I have appreciated your reporting and it has informed my decisions on these devices.


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