AfibAlert Versus AliveCor/Kardia: Which Mobile ECG Device Is Best At Accurately Identifying Atrial Fibrillation?

The skeptical cardiologist has been testing the comparative accuracy of two hand-held mobile ECG devices in his office over the last month. I’ve written extensively about my experience with the AliveCor/Kardia (ACK) device here and here. Most recently I described my experience with the Afib Alert (AA) device here.
Over several days I had my office patients utilize both devices to record their cardiac rhythm and I compared the device diagnosis to the patient’s true cardiac rhythm.


In 14 patients both devices correctly identified normal sinus rhythm. AFA does this by displaying a green check mark , ACK by displaying the actual recording on a smartphone screen along with the word Normal.
The AFA ECG can subsequently uploaded via USB connection to a PC and reviewed in PDF format. The ACK PDF can be viewed instantaneously and saved or emailed as PDF.

Normal by AFA/Unreadable or Unclassified by AliveCor

In 5 patients in normal rhythm (NSR) , AFA correctly identified the rhythm but ACK was either unreadable (3) or unclassified (2). In the not infrequent case of a poor ACK tracing I will spend extra time adjusting the patient’s hand position on the electrodes or stabilizing the hands. With AFA this is rarely necessary.

In this 70 year old man the AFA device recording was very good and the device immediately identified the rhythm as normal.
Chaput AFA SR
ACK recording was good quality but its algorithm could not classify the rhythm.
GC Unclassified
A 68 year old man who had had bypass surgery and aortic valve replacement had a very good quality AFA recording with correct classification as NSRChaput AFA SR
AliveCor/Kardia recordings on the same patient despite considerable and prolonged efforts to improve the recording were poor and were classified as “unreadable”

Scott AC unreadable
Alivecor tracing shows wildly varying baseline with poor definition of p wave


False Positives

There were 3 cases were AFA diagnosed atrial fibrillation (AF) and the rhythm was not AF. These are considered false positives and can lead to unncessary concern when the device is being used by patients at home. In 2 of these ACK was unreadable or unclassified and in one ACK also diagnosed AF.

A 90 year old woman with right bundle branch block (RBBBin NSR was classified by AFA as being in AF.

VA AFA read as AF
Slight irregularity of rhythm combined with a wider than normal QRS from right bundle branch block and poor recording of p waves likely caused AFA to call this afib

VA unclassified RBBB
AliveCor tracing calls this unclassified. The algorithm does not attempt to classify patients like this with widened QRS complexes due to bundle branch block.

The ACK algorithm is clearly more conservative than AA. The ACK manual states:

If you have been diagnosed with a condition that affects the shape of your EKG (e.g., intraventricular conduction delay, left or right bundle branch block,Wolff-Parkinson-White Syndrome, etc.), experience a large number of premature ventricular or atrial contractions (PVC and PAC), are experiencing an arrhythmia, or took a poor quality recording it is unlikely that you will be notified that your EKG is normal.


One man’s rhythm confounded both AFA and AC. This gentleman has had atrial flutter in the past and records at home his rhythm daily using his own AliveCor device which he uses in conjunction with an iPad.IMG_8399.jpg
During our office visits we review the recordings he has made. He was quite bothered by the fact that he had several that were identified by Alivecor as AF but in fact were normal.
Screen Shot 2017-05-06 at 11.48.47 AM
These are recordings Lawrence made at home that i can pull up on my computer. He makes a daily recording which he repeats if he is diagnosed with atrial fibrillation. In the two cases above of AF a repeat measurement was read as normal. Of the two cases which were unclassified , one was normal with APCs and the other was actually atrial flutter

A recording he made on May 2nd at 845 pm was read as unclassified but with a heart rate of 149 BPM. The rhythm is actually atrial flutter with 2:1 block.
Screen Shot 2017-05-06 at 11.47.37 AM
Sure enough, when I recorded his rhythm with ACK although NSR (with APCS) it was read as unclassified
Screen Shot 2017-05-06 at 11.49.49 AM
AFA classified Lawrence’s rhythm as AF when it was in fact normal sinus with APCs.
AFA Mcgill AF

One patient a 50 year old woman who has a chronic sinus tachycardia and typically has a heart rate in the 130s, both devices failed.
We could have anticipated that AC would make her unclassified due to a HR over 100 worse than unclassified the tracing obtained on her by AC (on the right)was terrible and unreadable until the last few seconds. On the other hand the AFA tracing was rock solid throughout and clearly shows p waves and a regular tachycardia. For unclear reasons, however the AFA device diagnosed this as AF.


Accuracy in Patients In Atrial Fibrillation

In 2/4 patients with AF, both devices correctly classified the rhythm..

In one patient AFA correctly diagnosed AF whereas ACK called it unclassified.
This patient was in afib with HR over 100. AFA correctly identified it whereas ACK called in unclassified. The AC was noisy in the beginning but towards the end one can clearly diagnose AFScreen Shot 2017-05-06 at 8.39.06 AMScreen Shot 2017-05-06 at 8.11.53 AM
In one 90 year old man AFA could not make the diagnosis (yellow)
Screen Shot 2017-05-06 at 11.35.40 AM
ACK correctly identified the rhythm as AF
Screen Shot 2017-05-06 at 11.37.51 AM
One patient who I had recently cardioverted from AF was the only false positive ACK. AliveCor tracing is poor quality and was called AF whereas AFA correctly identified NSR>
Screen Shot 2017-05-06 at 8.42.46 AMScreen Shot 2017-05-06 at 8.42.26 AM

Overall Accuracy

The sensitivity of both devices for detecting atrial fibrillation was 75%.
The specificity of AFA was 86% and that of ACK was 88%.
ACK was unreadable or unclassified 5/26 times or 19% of the time.

The sensitivity and specificity I’m reporting is less than reported in other studies but I think it represents more real world experience with these types of devices.


In a head to head comparison of AFA and ACK mobile ECG devices I found
-Recordings using AfibAlert are usually superior in quality to AliveCor tracings with a minimum of need for adjustment of hand position and instruction.
-This superiority of ease of use and quality mean almost all AfibAlert tracings are interpreted whereas 19% of AliveCor tracings are either unclassified or unreadable.
-Sensitivity is similar. Both devices are highly likely to properly detect and identify atrial fibrillation when it occurs.
-AliveCor specificity is superior to AfibAlert. This means less cases that are not AF will be classified as AF by AliveCor compared to AfibAlert. This is due to a more conservative algorithm in AliveCor which rejects wide QRS complexes, frequent extra-systoles.
Both companies are actively tweaking their algorithms and software to improve real world accuracy and improve user experience but what I report reflects what a patient at home or a physician in office can reasonably expect from these devices right now.


19 thoughts on “AfibAlert Versus AliveCor/Kardia: Which Mobile ECG Device Is Best At Accurately Identifying Atrial Fibrillation?”

  1. I bought the 6 lead Kardia Mobile device and always get tachycardia or Normal Sinus Rhythm results. The other day I got Afib and sent it to them for a cardiologist to review. Their cardiologist said Normal Sinus Rhythm. It was a false positive. I was later told y them when I inquired as to why that would happen my P wave is too small on lead I. So I’m no longer worried about Afib, but now I’m a little concerned what having a small P wave might be due to. They said if it always looks like that on my recordings they’ll offer a refund as the device isn’t for people like me. I looked at old recordings and that lead I does indeed look different from other people’s readouts, with mine being choppy and small with no real big pointy spike ups. Does this mean I only risk getting false positive afib results if I keep it, or would I be in danger of false negatives?

    • I’ve written about this a lot. I think most recently on a post entitled something like “what is the cause of inconclusive readings…”
      The solution is to put your device in single lead mode, put your right hand on the right electrode and put the left electrode on the top of your left knee. This will create a lead II that AliveCor has to analyze.
      let me know if that works for you.

  2. I know this thread is about a year old, but one thing that has made a difference for us (not so pleasantly): my husband’s cardiologist insisted on afibalert — would not work with any other device other than an implantable which my husband was not a fan of. So that’s the one we got. But it has two major drawbacks: one, it cannot connect without a WINDOWS based computer. We are an apple household; I had to go to work and ask my boss if I could use her personal windows computer (it requires a software download to work, so you can’t use a public computer such as the library) to upload his file so the cardiologist could look at it. They claim (for over a year now) to be “working” on a workaround for apple computers but have not gotten around to it. SO, we can neither upload nor see the strip, nor can we email it to anyone, without a windows computer. I’m not happy — I am a paramedic and can read EKG’s but this thing doesn’t allow us access to the strip in real time. I could go out and BUY a windows computer I suppose, but the afibalert device was not exactly cheap, adding the cost of a computer on top of that is a serious drag. Yes, he gets mostly green lights which means probably no afib… but the few times that it is not sure, or it thinks there is afib (he has frequent PVC’s) we are at least a few DAYS away from being able to analyze it or send it. Bummer.

    • Cheryl,
      thanks for the comments.
      I, too, am a Mac person and found the need for a Windows based computer to be a major limitation.
      I have worked with a prototype this company has which communicates by BlueTooth with iPad or iPhone so that one can instantly see the tracings. That will be a big step forward for afib alert.
      I am somewhat confused by your opening sentence-why did the cardiologist insist on afibalert?
      Also, you mentioned two major drawbacks but I can only find one described.

      • sorry that my email following didn’t alert me to your response and I just found it now! The two issues I had with it are related; we cannot upload it for the doc to look at AND I cannot see it to read it myself for the same reason — can’t upload it. I am a paramedic, not a cardiologist, but have been reading EKG’s for a long time and am confident in my own ability to interpret the “unknown” or possible false positives if I can get a look at it. Since then we picked up the Kardia watch band for his Apple Watch. He almost always (like, 99.9%) gets his episodes in the middle of the night when he has to put the watch ON to check though. All but one of the worried-and-so-checked episodes during the day have been just PVC’s and usually the Kardia gets it right; when it is unsure I can see it. anyway, with the Kardia he can email me a strip (which is better quality and larger than peering at it on his watch) and I can look at it on my phone. That has solved a lot of issues. The doc’s insistence on afibalert was, according to him, because he did not “trust” any of the other versions and in fact called them all “junk”. It could also have been because he was in on the development of the afibalert device, although he insisted that he gets no funds from it. Anyway, the sad fact is that the afibalert kept promising a Mac-friendly upload but never delivered, so although he still uses it as a cross-check (especially when I’m not around) it isn’t useful for its full intended purpose.

        • I’m not sure what is going on with AfibAlert these days but I no longer am receiving communications from them on a move to making it work with a SmartPhone.
          Personally, because of the clunkiness of the interface and in downloading and viewing the tracings I have abandoned using it and exclusively use Kardia in my office and with my patient home monitoring.

  3. I have been using the Kardia mobile. I get these strange feelings in my chest ( i guess they are palpitations?!) often and do a recording and while recording and I feel these “palpitations” I also see it on the Kardia. Yet the Kardia marks the ecg as normal. I know it isn’t normal.
    I wish I could explain what’s going on. Just don’t know all the terminology of an ecg. In between 2 qrs waves I am getting 2 waves(pointy) very close to each other but they are pointing down. Any idea of what this could be? Thank you.

  4. I’ve been using Alivecor for a few months. It’s not reliable at all, so I mostly use it to see my heart rate, which I like to see when I’m in an episode. They kept sending me push notifications to buy premium so I bought it and didn’t get it. I have a $106. bill on my credit card, but customer service (it took many calls) tells me I don’t have the service. That’s right. That’s why I’m calling. I guess I will protest the charge on my credit card, which is fine. But, I don’t see that, according to this data you have, that either app is very good. Does the Afa you describe have a more transparent account system? Better customer service? At this point, I just want good customer interface. At Alivecor/Kardia, customer service is so awful — trying to work with a bad system — and not the sharpest tacks in the toolbox, that I just want a good user experience. I know these systems will some day have competition as well as improved ECG readings. I guess all customers are currently in beta testing.

    • I keep it in my wallet, making sure nothing is bending it or touching the leads. I also bought the Kardia Band for my Apple watch. I had to order it from Europe off eBay, since it’s not available in the US yet. The Kardia Band seems to have issues getting a good tracing occasionally. The Apple Watch Series 3 Heart Health Study is going to work on detecting AFib and arrhythmias and the QardioCore, which is a 3 lead, should be released soon, though I’m not sure if there will be anytype of automated detection of rhythms. Both are pretty exciting. I wish the FDA could keep up with consumer biotech field.

      • I paid ~$150 for the Kardia Band. The Kardia band works in the US with the Phone App, but will not let you use the Apple Watch app.
        I very much appreciate your evidence based site also. Thanks!


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