Since it is common for AF to present at rates >120 BPM, AW ECG will fail to notify many (if not most) of its users that they are in AF.
AliveCor’s Kardia mobile ECG device (both the single lead and the six lead), on the other hand, has no problems identifying AF >120 BPM. I have found that the Kardia ECG was highly accurate in patients with rapid AF from using the device in hundreds of my patients since 2013.
After writing about the AW AF flaw I opened my KardiaPro dashboard which connects to the online ECG recordings each of my patients has made.
Two of my patients with paroxysmal AF had gone into AF in the last 2 days and made recordings.
Both of them had rates > 120 BPM. In both cases, Kardia had easily made the diagnosis. AW would have declared these “inconclusive.”
Patients should be aware of this AW AF flaw. The absence of a declaration of possible AF on the AW ECG should not reassure anyone of the absence of AF.
AW users should have their high rate recordings reviewed by a cardiologist.
Alternatively, they could purchase a Kardia device and utilize it for heart rates over 120 BPM.
In less than a month AliveCor plans to release its KardiaMobile 6L which will provide 6 ECG leads using a smartphone based mobile ECG system that is similar to the Kardia single lead system.
AliveCor’s website proclaims “This is your heart x 6.”
I was fortunate enough to obtain a demo version of the 6L and have been evaluating it.
My first impressions are that this is a remarkable step forward in the technology of personal ECG monitoring. I’m not sure if I would call it “your heart x 6” but I feel the ability to view six high quality leads compared to one is definitely going to add to the diagnostic capabilities of the Kardia device.
Kardia 6L Setup And Hardware
The 6L is similar in design and function to the single lead device.
I’m including this cool spinning video (from the AliveCor website) which makes it appear, slick, stylish and futuristic
Once paired to the Kardia smartphone app (available for iOS or Android smartphones for free) it communicates with the smartphone using BLE to create ECG tracings.
Like the single lead Kardia the 6L has two sensors on top for left and right hand contact. But in addition, there is a third on the bottom which can be put on a left knee or ankle.
The combination of these sensors and contact points yield the 6 classic frontal leads of a full 12 lead ECG: leads I, II, III, aVL, aVR, and aVF. This is accomplished, AliveCor points out “without messy gels and wires.
I found that using the device was simple and strait-forward and we were able to get high quality tracings with minimal difficulty within a minute of starting the process in all the patients we tried it on.
The Diagnostic Power Of Six Leads
Below is a tracing on a patient with known atrial fibrillation. The algorithm correctly diagnoses it. With 6 different views of the electrical activity of the atrium I (and the Kardia algorithm) have a better chance of determining if p waves are present, thereby presumably increasing the accuracy of rhythm determination
Depending on the electrical vector of the left and right atria, the best lead to visualize p waves varies from patient to patient, thus having 6 to choose from should improve our ability to differentiate sinus rhythm from afib.
In the example below, the Kardia 6L very accurately registered the left axis deviation and left anterior fascicular block that we also noted on this patient’s 12 lead ECG. This 6L capability, determining the axis of the heart in the frontal plane, will further add to the useful information Kardia provides.
For a good summary of axis determination and what abnormal axes tells us see here.
The History of ECG Leads
When I began my cardiology training the 12-lead ECG was standard but it has not always been that way. I took this timeline figure from a nice review of the history of the ECG
Einthoven’s first 3 lead EKG in 1901 was enormous.
It is mind-boggling to consider that we can now record 6 ECG leads with a smartphone and a device the size of a stick of gum
For the first 30 years of the ECG era cardiologists only had 3 ECG leads to provide information on cardiac pathology. Here’s a figure from a state of the art paper in 1924 on “coronary thrombosis” (which we now term a myocardial infarction) showing changes diagnostic of an “attack” and subsequent atrial fibrillation
In the 1930s the 6 precordial leads were developed providing more information on electrical activity in the horizontal axis of the heart. The development of the augmented leads (aVr, aVL, aVF) in 1942 filled in the gaps of the frontal plane and the combination of all of these 12 leads was sanctified by the AHA in 1954.
I’ll write a more detailed analysis of the Kardia 6L after spending more time using it in patient care.
Specifically I’ll be analyzing (and looking for published data relative to):
-the relative accuracy of the 6L versus the single lead Kardia for afib determination (which, at this point would be the major reason for current Kardia users to upgrade.)
-the utility of the 6L for determination of cardiac axis and electrical intervals in comparison to the standard 12 lead ECG, especially in patients on anti-arrhythmic drugs
For now, this latest output from the meticulous and thoughtful folks at AliveCor has knocked my socks off!
N.B. If one uses the single lead kardia device in the traditional manner (left hand and right hand on the sensors) one is recording ECG lead I. However, if you put your right hand on the right sensor and touch the left sensor to your left leg you are now recording ECG lead II and if to the right leg, ECG lead III.
I describe this in detail here. For certain individuals the lead II recordings are much better than lead I and reduce the prevalence of “unclassified” recordings.
My feeling is that by automatically including the leg (and leads II and III) the 6L will intrinsically provide high voltage leads for review and analysis, thereby improving the ability to accurately classify rhythm.
And (totally unrelated to the 6L discussion) one can also record precordial ECG leads by putting the device on the chest thus theoretically completing the full 12 leads of the standard ECG.
Please also note that I have no financial or consulting ties to AliveCor. I’m just a big fan of their products.
The Skeptical Cardiologist is a strong proponent of empowering patients with atrial fibrillation by utilizing personal cardiac rhythm devices such as Afib Alert or AliveCor’s Kardia.
I’ve written about my experiences with the initial versions of the Kardia mobile ECG device and the service it provides here and here.
I have been monitoring dozens of my afib patients using AliveCor’s Physician Dashboard.
Recently AliveCor changed fundamentally the way their app works such that for new users much of the functionality I described in my previous posts now requires subscribing to their Premium service which costs $9.99 per month or $99 per year.
What Has Changed With The Kardia App
The Kardia device which works with both iOs and Android smart
phones is unchanged and still generates a “medical-grade” single lead rhythm strips which appears within the Kardia app.
The app still is reasonably accurate at identifying atrial fibrillation or normal heart rhythms and offers a fee-based service for interpretation of unclassified ECGs.
However, for new purchasers of Kardia, the capability to access, email or print prior ECG recordings has gone away. Prior to March of this year, Kardia users could access prior ECG tracings which were stored in the cloud by touching the “Journal” button on the app. These older tracings could be emailed and they were available through the cloud for a physician like myself to review at any time.
Now new Kardia purchasers will find that when they make an ECG recording they have the option to email a PDF of the ECG but once they hit the DONE button it is gone and is not stored anywhere.
For my patients purchasing after March, 2017 this means that unless they purchase Kardia Premium service I will not be able to view their ECG recordings online.
An AliveCor account executive summarized for me the changes as follows:
We added a significant number of features over the past year and a half, and grandfathered all users on March 16th, 2017. New users now have the option to download and use Kardia for free, but the premium services are $9.99/mo or $99/year. Kardia Premium allows unlimited storage and history of their EKGs, summary reports with longitudinal data, blood pressure monitoring and tracking weight and medication.
Why Journal Functionality Is Important
If you purchased your AliveCor/Kardia device prior to March 16th, 2017 ago the journal functionality still works. Let’s call such customers “Journal Grandfathered”.
This Journal functionality is important in a number of ways:
My Journal Grandfathered patients can bring their phones with them during an office visit and we can review all of their ECG tracings.
Journal gGandfathered Kardia users can email their old tracings to their physicians or to anyone they wish (even the skeptical cardiologist!). They can also print them out and save PDFs of the tracings.
I can view through my online physician account all of my Journal Grandfathered patients. This means any time a patient of mine makes a recording that is unclassified or suggests atrial fibrillation I can be notified and immediately view it online.
This fundamental change took place as AliveCor attempts to convince purchasers of the Kardia device to use their Premium service.
Why AliveCor Changed The Kardia App Function
Dr. David Albert, inventor and cardiologist and the founder of AliveCor was kind enough to talk with me about this change.
He indicates that of the 150,000 AliveCor users, 10,000 are now using the Kardia Premium service. About 20% of new users elect Kardia Premium.
Prior to the change all AliveCor users had their old ECG recordings stored in the cloud in a HIPPA compliant fashion. This free service was costing AliveCor quite a bit and the company felt it was best to switch to a subscription service to provide this secure cloud storage.
With the change to the (relatively inexpensive) subscription service, patients will get additional features. As the AliveCor account executive described:
Kardia Premium allows unlimited storage and history of their EKGs, summary reports with longitudinal data, blood pressure monitoring and tracking weight and medication.
I’ve looked at the Premium service and it seems quite useful when combined with a connected physician utilizing Kardia Pro. I’ll evaluate the Premium service and the physician Kardia Pro service further and write a full post on its features in the near future.
If you are not grandfathered and want to stick with the Basic Kardia service you still have an immensely useful and inexpensive device which allows personal detection of your cardiac rhythm. Just remember to email yourself the ECG recording you just made before you hit DONE.
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.
ACK recording was good quality but its algorithm could not classify the rhythm.
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 NSR
AliveCor/Kardia recordings on the same patient despite considerable and prolonged efforts to improve the recording were poor and were classified as “unreadable”
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.
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.
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.
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.
Sure enough, when I recorded his rhythm with ACK although NSR (with APCS) it was read as unclassified
AFA classified Lawrence’s rhythm as AF when it was in fact normal sinus with APCs.
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 AF
In one 90 year old man AFA could not make the diagnosis (yellow)
ACK correctly identified the rhythm as AF
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>
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.
I’m writing this brief post as a warning to any individuals who have purchased the smartphone app AF Detect (screen shot below from Apple app store.) It is not a reliable detector of atrial fibrillation (AF).
A patient of mine with AF recently purchased this app unbeknownst to me. He relied on its faulty information which reassured hm he was not in AF when in fact he was in AF. Such misinformation has the potential to lead to dangerous delays in diagnosis.
There are multiple reviews on the Apple and Google app sites which confirm the total lack of reliability of this app to diagnose AF with multiple instances of both failure to detect known AF and inappropriate diagnosis of AF when rhythm was not AF.
In the description of the app the company says the app will “transform you rmobile device into a personal heart rate monitor and atrial fibrillation detector”.
However after purchasing the app and before using it you see this disclaimer which states it is not to be used for any medical diagnosis.
I will be performing a more detailed analysis of this app’s performance in the future and contacting the FDA about the danger such inaccurate medical testing confers on victims.
In the meantime if you have any experience with this app or other apps claiming to detect AF reliably using detection of the pulse from finger application to the camera lens please share them with me (via email DRP@theskepticalcardiologist.com or via comments below.)