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A Comparison of Alivecor’s Kardia 6L and Kardia Single Lead Mobile ECG With and Without the V2 Algorithm

The skeptical cardiologist has long been an advocate of the Kardia single lead mobile ECG for personal monitoring of cardiac rhythm. In conjunction with the KardiaPro dashboard, it drastically reduces the need for expensive long-term monitoring and has reduced the need for ED visits and hospitalizations for many of my patients.

Although I welcomed the Alivecor’s six-lead version of Kardia and found it to be a marvel of modern engineering, I had heretofore not found compelling reasons to recommend it to my patients over the less expensive single lead.

A reader, John Lorscheider, who has used the single-lead Kardia for 5 years to monitor his atrial fibrillation has provided me with his excellent detailed comparison of the 6L to the single lead. In addition, he has upgraded to the V2 algorithm (which I discuss here) and provides some excellent comparative information on the performance of both the single lead and six lead devices with this upgrade versus V1.

Of note, John writes “The V2 upgrade and other extra features are only available with the KardiaCare Membership.” Most of my patients are already paying $99/year for the premium service which allows storage of their ECGs in the cloud and allows me to view all ECGS and Omron BPs on my KardiaPro dashboard and I assume they will have or will be transitioned to the KardiaCare Benefits. (Alivecor please confirm.) What follows is John’s personal rhythm history followed by his analysis.

First a bit of background. I was initially diagnosed 5 years ago with AFIB.  I was entirely asymptomatic at that time and the AFIB was coincidentally picked up in a routine physical by my internist.  After a complete workup, I was labeled with paroxysmal AFIB and hyperthyroidism. Once the thyroid issue was corrected, I returned to sinus rhythm, at least for a while.  I’ve used the Kardia single-lead device for 5 years now to spot check for AFIB.  My paroxysmal AFIB has only been detected in a clinical setting once over 5 years.  With the Kardia device, I detected AFIB dozens of times in my home.  I can just print out the EKG and hand it, email it or upload it to my cardiologist’s EMR patient portal, MyChart, if I need to.  Faced with the prospect of untreated and potentially advancing AFIB to persistent or permanent status, the purchase of the Kardia unit was a no-brainer.
In the past year, I began experiencing frequent tachycardia spikes (180-200 BPM) when I was cycling at a normal 130-140 BPM zone while endurance cycling according to my Polar H10 heart rate sensor and Polar Beat iPhone App.  I also made an appointment with my cardiologist who did a complete workup and everything checked out fine,  He fitted me with a 5-day event monitor and the abnormal results while cycling correlated nicely with my heart rate monitor’s activity.  He attributed the tachycardia to exercise-induced adrenaline surge. 
However, the echo showed that I also developed a severely enlarged left atrium which I didn’t have 5 years ago.  That dilation was likely due in part to the high intensity and long duration of frequent endurance cycling and running which I have done for may decades, and perhaps the AFIB as well.  The AFIB has returned and is now very symptomatic.  The single lead Kardia works very well for AFIB determination but it has some drawbacks.  I’ve been on Metropolol (daily), Flecainide (pill-in-a pocket) and Eliquis which works well, along with a reduced training load and a few lifestyle tweaks.  Perhaps my endurance exercise finally caught up with me at age 67. 
I recently purchased the Kardia 6L device to compare with the Kardia single-lead device and upgraded to the Kardia app with the V2 algorithm.  These are my comparisons between the two:
Kardia Single Lead Device with Version 1 Algorithm:

  1. Highly accurate for diagnosing: 
    • AFIB 
    • Bradycardia
    • Tachycardia detection to 300 BPM (Originally was only to 100 BPM)
    • Indicates current heart rate
  2. You can email yourself an EKG and print it out or email it to your cardiologist
  3. Stores your EKG’s on your SmartPhone (uses almost no smartphone memory)
  4. Device runs a onetime $89
  5. SmartPhone App is free of charge


  1. Very prone to electrical interference from appliances, TV’s, radios, computers, etc. making the Kardia recording “Unreadable”.  It’s sometimes hard to find a “quiet” place without interference.
  2. The single lead device needs to access the microphone on smartphones and cannot be used when a person is wearing BlueTooth enabled hearing aids.  The hearing aids must first be turned off in order to do a recording.
  3. The single lead device must be positioned with 1-2” of the phone’s microphone to make a recording.  Any further away it will not connect with the phone.
  4. This is a desktop device and not wearable so it can’t be used during exercise.

Kardia Single Lead Device with Version 2 Algorithm:

  1. Same Pros as above plus:
  2. The V2 upgrade performs all of the V1 functions above along with the following “Advanced Determinations” that previously were labeled as “Unclassified”
    • Sinus Rhythm with Premature Ventricular Contractions (PVCs).  I get a few of these and they seem quite benign.
    • Sinus Rhythm with Supraventricular Ectopy (SVE)
    • Sinus Rhythm with Wide QRS
  3. Stores the EKG’s in AliveCor’s cloud
  4. The V2 upgrade and other extra features are only available with the KardiaCare Membership


  1. Same cons as above plus:
  2. The V2 algorithm upgrade with the “Advanced Determinations” is not free and costs $99 per year for an annual membership.  It’s worth it for me, but maybe not everybody.  $99 wouldn’t buy me a seat in my cardiologists waiting room, much less an office follow-up visit to see him.
  3. You get a host of added features with a membership, but some are useful and some are not.

Kardia 6L Six Lead Device with Version 2 Algorithm Pros:

  1. Same Pros as above plus:
  2. The 6L communicates with smartphones via BlueTooth with a simple discrete device pairing.  It does not communicate by sound with the smartphone’s microphone like the single lead Kardia unit does.  This allows for a greater distance capability between the 6L and the SmartPhone. 
  3. The 6L appears less prone to electrical interference 
  4. The 6L device has an advantage over the single lead device in that BlueTooth hearing aid wearers don’t have to turn off the hearing aids prior to taking a reading.  I suspect many Kardia users may wear hearing aids too.
  5. AliveCor’s website states: “FDA-cleared and doctor recommended: The most clinically validated 6-lead personal EKG, FDA-cleared to detect AFib, Bradycardia, and Tachycardia.”  Wait a minute, that’s what the single lead Kardia device does!  Color me skeptical. 


  1. AliveCor doesn’t appear to provide a clear explanation of what the 6-lead diagnostic advantages are for either the doctor or the patient.  Two cardiologists I spoke with don’t see the advantage of the 6-lead device over the single lead device either.  This makes me even more skeptical.  Perhaps you or one of your followers could enlighten me.
  2. The 6L is costlier at $149 and for V2 algorithm requires a $99 annual membership.  OK, I’ll pay it just because of the greater range, less interference, and being able to keep my BlueTooth hearing aids on when I take a recording.

John Lorscheider lives in Southeast Wisconsin and he and his wife and are now retired. He was in sales, engineering and and senior management for industrial pumps and fluid process equipment for various manufacturers for 40 years. 
He has also written for and moderated several web medical forums in his spare time.  His leisure time is spent between cycling, running, traveling, cooking, enjoying family and friends, listening to music, along with reading and finding the many biases and flaws in medical trials.

Skeptically Yours,


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