Are Your Apple Watch ECG Recordings Consistently Inconclusive? Here’s One Way To Fix It

Personal ECG devices like Apple Watch and Kardia are wonderful for most people at recording a single-lead ECG and determining cardiac rhythm. With both devices, however, it is not uncommon to get an inconclusive (Apple’s term) or unclassified (Alivecor’s term) reading at times.

I’ve discussed some fixes for Kardia here. Often recordings can be drastically improved by moistening the skin contacting the two electrodes, thereby improving the conductance of the electrical signal. Minimizing movement helps many cases. But for some, this is the norm no matter how elaborately fingers are lubricated or how aggressively motion is eliminated.

A reader emailed me with his very frustrating case which typifies this problem:

Not sure if you can help me but I wanted to reach out based on a post I saw from you on line. I have advanced CAD (CT scan calcium score of 2300) and purchased an apple watch 5 about a year ago to be able to monitor my heart rate and do ECGs.  I am unable to get a consistent Sinus Rhythm even though I know I have a normal ECG.  

In fact the display when I am taking an ECG is all over the map – many times it looks like a three year old coloring with a crayon.  I have worked with Apple support, they sent a new watch but the same issues.  I then was asked to submit my data file to engineering after i replicated the issue, and that was done in February.  Now when I call support they basically tell me “dont call us we will call you” and the standard answer is “engineering is still looking into it”.

 I am convinced there is something with me physiologically that prevents the watch from doing consistent ECGs with me.  I believe Apple engineering knows there is a deficiency and no solution so just ignoring it. I am not sure what recourse I have other than to try and find others with similar issues and go down a class action lawsuit rat hole.  I was curious though if you had come across this issue in the past and/or you know of groups that might be organizing to pursue some type of action from Apple

I asked him to send me examples of his inconclusive Apple Watch (AW) ECGs and it was clear that this individual (we’ll call him Don) suffered from what I term “Low Lead I Voltage Syndrome.”

Here’s a typical recording for him. Note that the squiggles that correspond to electrical activation of the ventricles (the QRS complexes) can be barely be discriminated from the background noise of the tracing. Understandably, the AW algorithm can make neither heads nor tales of such a scribble. Even the skeptical cardiologist, who prides himself on interpreting the most difficult of single-lead ECG rhythms cannot be sure this is normal.

Lead I Apple Watch recording. The QRS complexes are microscopic in size, reaching about 2 mm

A very large percentage of his overall recordings were inconclusive but all of them demonstrated this problem with extremely low amplitude (or voltage) of the standard Lead I AW tracing.

We have seen this same problem with Kardia single-lead ECG recordings and have discussed the cure. It was not fixed by moistening or lubricating either the back of the wrist of the right fingertip.

I instructed Don to try making a recording with the AW on his left knee, preferably a flat, non-hairy portion, as opposed to his wrist. I told him that sometimes the heart is vertically oriented in the chest (often seen in thin individuals) and the leg works better. 

This is where the AW ended up for Don. Back of AW on top of the left knee. Tip of right index finger then touches crown to activate ECG recording.

From this spot, Don’s ECG recordings were dramatically improved and never inconclusive. The amplitude of the QRS complexes increased from 2 to 16 mm!

ECG Lead II recording from left knee. The ECG QRS spikes are now 16 mm tall.

I’m going to call this manner of recording the “Albert maneuver” as Alivecor’s Dr. David Albert first showed it to me.

My reader was right there was something about him that was different. Not wrong and not his physiology or cardiac rhythm. Just a normal variation in his anatomy which led to a vertically oriented heart.

Don informed me that he was thin: “6 foot 3 inches and 165 pounds soaking wet” to be precise.

If you’re getting great recordings with high amplitude QRS complexes and AW or Kardia is still reading inconclusive or unclassified then you likely are having frequent PVCs or PACs, something Kardia plans to address with its soon to be released AI V2.

Apple engineering presumably consists of the brightest minds in the industry. It’s surprising that they don’t know about the “Low Lead I Voltage Syndrome” and its curative Albert maneuver. They could save many AW wearers from experiencing the dreaded “inconclusive” categorization and cut down on Apple support costs.

Conclusively Yours,


For more discussion on reducing unclassified single lead ECG recordings from Kardia and the advantages of Lead II see my prior post here.


15 thoughts on “Are Your Apple Watch ECG Recordings Consistently Inconclusive? Here’s One Way To Fix It”

  1. Hello,

    First of all, this trick with the leg is amazing. Prior to learning about this, I have only ever had low voltage readings on my Kardia mobile 1 lead. My question is, Kardia has said atrial fibrillation 24 times on my low voltage readings over the last few months. Is it possible for low voltage to be mistaken as afib? I did submit 1 of the readings to the cardiologists who read for them, and their response was “possible abnormal heart rhythm due to an irregularly irregular discharge.” I am scheduled to see a cardiologist, but just curious if all these readings could be wrong. Thank you!

    • Katie,
      Great to hear.
      Kardia does not often call afib incorrectly but low voltage p waves is one circumstance.
      The reading from the cardiologist at Alivecor was not particularly helpful.
      Send me a tracing.
      Dr. P

  2. Omg it worked. My wrist readings have been more distinctive than the ones shown in your article, however the spikes in my readings were only ever downward and weren’t just inverted… they were bizarre in many ways. First time I tried it on my left knee is the first time it looked like an actual heart rhythm.

  3. I am so grateful to have found your website. In 2017, I blacked out while driving and had a complete cardiac work-up but A Fib not found. (Event monitor did have findings of PACs, PVCs, atrial couplets, bradycardia, atrial runs, tachycardia, and ventricular couplets.) I got an Apple watch not too long after that because I felt like something wasn’t right. (The most unsettling heart sensation I have had is that of my heart “doing a flip” but it only happens once or twice a year and it didn’t happen while wearing the monitor.) Recently, I had a funny and new feeling with my heart that lasted (off and on) all day and I haven’t ever experienced these feelings for that duration so it worried me a bit. I took several ECG readings with my watch during that day and they were all inconclusive. I am trying to figure out if this was just more of the same “variants” (?) so that I can avoid a $7k bill if it isn’t necessary. Any thoughts? Your help would be much appreciated, Louise

  4. I throw frequent pvcs and get a sinus rhythm maybe 50% of the time. I tried the leg option but didn’t work for me. My cardiologist isn’t worried so I don’t bother using that feature anymore.

  5. Thank you for this article! The ECG of my Watch 4 was driving me nuts. I actually switched to a Fitbit Sense in the meanwhile and there the readings can be interpreted almost always. However, the method of the Sense is that it has two divided areas which you press with two fingers instead of one small area on a crown. Your method improves the reads of the Sense as well though!

    I’m 6`7 at 165 pounds so yeah: tall and pretty skinny 🙁

  6. Dr. Pearson —

    I am a 70-year-old female, generally healthy, no medications. My Apple Watch ECG is almost always inconclusive but I tried the knee measurement that you recommended and it comes back with a nice “Sinus Rythym” every time. I don’t understand the “vertical heart” terminology you used, and if I do have vertical heart does that have any health implications for me or is it just something that affects the measurement technique?

    • Gul,
      So glad that my “trick” worked for you.
      No health implications that we are aware of. It is associated with thin or tall body types so that type generally fares better than the obese type.
      Your question may inspire me to see if I can find anything on the vertical heart. I tried previously without success.
      Dr P

  7. Dear Dr. Anthony Pearson,

    I’ve been diagnosed with an Aortic Aneurism, I have some chest pain after exercises and I have some ECG devices at home, to help me keep my hear rate under check also. Namelly:
    – a Withings Scanwatch (to me better option than Apple Watch since it works on Android)
    – a Withings BP monitor with ECG functionality
    – and the Kardia 6L

    But most of them don’t show such ECG “clean” lines as your examples, and with the Kardia 6L, I’m never sure If I should use “enhanced mode” or not, to “clean” the ECG lines? What is your oppinion on Kardia’s enhanced mode ?

    Do 12 leads ECG monitors from Hospitals and Clinics also use some kind of “enhanced mode” algorithms to clear/clean the lines of the ECG Leads of some artifacts/noise, before printing?

    What do you recommend ? Should I try to take an ECG with the watch on my left knee also?

    I’m afraid the algorithms for the ECG (both Kardia and Withings) might be missing something, since the lines are not clean/clear to read…

    Really appreciate your help and possible reply and your articles !

    BTW: do you have/provide a service for analyzing ECG’s outputs? Or know of any reputable cardiologist providing that service online? Thanks

  8. I have lower lead I voltage recordings on my AW, but luckily mine can still be interpreted. My wife’s recordings are very even worse and are usually inconclusive. We’ve used the leg method several times in the past and it works great. Got the idea to do it from an article similar to the following about taking a multi lead reading with an AW.

    I do wonder what percentage of people have this low lead I voltage issue. It doesn’t seem to be the majority, but is it a sizable percentage?

    • Brad,
      Yes. There was a nice article on obtaining a 12 lead ECG with Apple Watch. I’ve been meaning to write about that.
      It is hard to know the % with “low voltage Lead I syndrome” but my estimate based on my patients is around 10%.
      If we take all individuals with >20% inconclusive recordings, however then we are dealing with a much higher prevalence.


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