The skeptical cardiologist has often sung the praises of the AliveCor Mobile ECG for home and office heart rhythm monitoring (see here and here.) However, there is a significant rate of failure of the device to accurately identify atrial fibrillation. I’ve seen numerous cases where the device read afib as “unclassified” and normal sinus rhythm (usually with PVCs or PACs) called afib both in my office and with my patient’s home monitors.
In such cases it is easy for me to review my patient’s recordings and clarify the rhythm for them.
For those individuals who do not have a cardiologist available to review the recordings, AliveCor offers a service which gives an option of having either a cardiac technician or cardiologist review the tracing. The “cardiac technician assessment” costs $9 and response time is one hour. The “Clinical Analysis and Report by a U.S. Board Certified Cardiologist” costs $19 with 24 hour response time.
Obviously, I have no need for this service but I’ve had several readers provide me with their anecdotal experiences with it and it hasn’t been good.
One reader who has a familial form of hypertrophic cardiomyopathy utilizes his AliveCor device to monitor for PVCs. One day he made the following recording which AliveCor could not classify:
He then requested a technician read which was interpreted as “atrial fibrillation sustained.”
He then had requested the cardiologist reading which came back as Normal Sinus Rhythm.
Finally, he again requested the technician read and got the correct reading this time which is normal sinus rhythm with PACs
When my reader protested to Kardia customer service about this marked inconsistency: three different readings in a 24 hour period, a Kardia customer service rep responded :
I was able to review this with our Chief Medical Officer who advised that the recording shows Sinus Rhythm with PACs. The Compumed report seldom provides identification of PACs and PVCs as most cardiologists believe they are not significant findings. The sustained AFib finding was incorrect, so I have refunded the $5 fee you had paid.
Please let us know if you have any other questions.
As I pointed out in my post on palpitations, most PVCS are benign but some are not and patients with palpitation would like to know if they are having PVCS and/or PACs when they feel palpitations.
More importantly, the misdiagnosis of afib when the rhythm is NSR with PACs or PVCs can lead to extreme anxiety.
Heres a recording
I made in my office this morning on a patient with cardiomyopathy and a defibrillator.
This is very clearly NSR with PVCs yet AliveCor diagnosed it as “possible atrial fibrillation.”
The AliveCor algorithm is not alone in making frequent errors in the diagnosis of atrial fibrillation.
The vast majority of ECGs performed in the US come with an interpretation provided by a computerized algorithm and medical personnel rely on this interpretation until it can be verified or corrected by an overreading cardiologist.
One study demonstrated that computerized ECG interpration (ECG-C) is correct only 54% of the time when dealing with a rhythm other than sinus rhythm
Another study found that 19% of ECG-C misinterpreted normal rhythm as atrial fibrillation. Failure of the physician ordering the ECG to correct the inaccurate interpretation resulted in change in management and initiation of inappropriate treatment, including antiarrhytmic medications and anticoagulation, in 10% of patients. Additional unnecessary diagnostic testing was performed based on the misinterpreted ECGs in 24% of patients.
When lives or peace of mind are at risk you want your ECG interpreted by a cardiologist.
I would like to take this opportunity to personally issue a challenge to IBM’s Watson.
Hey, Watson, I bet $1,000 I can Interpret cardiac rhythm from an ECG with more accuracy than you can!
If you feel your heart flip-flopping, then you are experiencing palpitations: a sensation that the heart is racing, fluttering, pounding, skipping beats or beating irregularly.
Often, this common symptom is due to an abnormal heart rhythm or arrhythmia.
The arrhythmias that cause palpitations range from common and benign to rare and lethal, and since most individuals cannot easily sort out whether they have a dangerous or a benign problem, they often end up getting cardiac testing or cardiology consultation.
The most common cause of palpitations, in my experience, is the premature ventricular contraction, or PVC (less commonly known as the ventricular ectopic beat or VEB).
The PVC occurs when the ventricles of the heart (the muscular chambers responsible for pumping blood out to the body) are activated prematurely.
This video shows the normal sequence of electrical and subsequent mechanical activation of the chambers of the heart.
To get an efficient contraction, the electrical signal and contraction begins in the upper chambers, the atria, and then proceeds through special electrical fibers to activate the left and right ventricles.
Sometimes this normal sequence is disrupted because a rogue cell in one of the ventricles becomes electrically activated prior to getting orders from above. In this situation, the electrical signal spreads out from the rogue cell and the ventricles contract out of sequence or prematurely.
This results in a Premature Ventricle Contraction.
I recorded the above AliveCor tracing in my office on a patient who suffers palpitations due to PVCs (we’ll call her Janet).
The wider, earlier beat (circled in red) in the sequence is the PVC. The prematurity of the PVC means that the heart has not had the appropriate time to fill up properly. As a result, the PVC beat pumps very little blood and may not even be felt in the peripheral pulse. Patients with a lot of PVCs, say ocurring every other beat in what is termed a bigeminal pattern, often record an abnormally slow heart rate because only one-half of the heart’s contractions are being counted.
While recording this, every time Janet felt one of her typical “flip-flops,” we could see that she had a corresponding PVC and the cause of her symptoms was made clear.
There is a pause after the PVC because the normal pacemaker of the heart up in the right atrium (the sinus node) is reset by electrical impulses triggered by the PVC.. The beat after the PVC is more forceful due to a more prolonged time for the ventricles to fill and Consequently, most patients feel this pause after the PVC rather than the PVC itself,
PVCs are common and most often benign. I have patients who have
thousands of them in a 24-hour period and feel nothing. On the other hand, some of my patients suffer disabling palpitations from very infrequent PVCs. From an electrical or physiologic standpoint, there seems to be neither rhyme nor reason to why some patients are exquisitely sensitive to premature beats.
How Do I Know If My PVCs Are Benign?
My patient, Janet, is a great example of how PVCs can present and how inappropriate or inaccurate heart tests done to evaluate PVCs can lead to anxiety and unnecessary and dangerous subsequent testing.
A year ago, Janet began experiencing a sensation of fluttering in her chest that appeared to be random. Her general practitioner noted an irregular pulse and obtained an ECG, which showed PVCS. He ordered two cardiac tests for evaluation of the palpitations: a Holter monitor and a stress echo.
A Holter monitor consists of a device the size of a cell phone connected to two sensors or electrodes that are stuck to the skin of the chest area. The electrical activity of the heart is recorded for 24 or 48 hours, and a technician then scans the entire recording looking for arrhythmias while trying to correlate any symptoms the patient recorded with arrhythmias. The Holter allows us to quantitate the PVCs and calculate the total number of PVCs occurring either singly or strung together as couplets (two in a row), or triplets (three in a row.)
Janet’s Holter monitor showed that over 24 hours her heart beat around 100,000 times with around 2500 PVCs during the recording. Unfortunately, the report did not mention symptoms, so it was not possible to tell from the Holter if the PVCs were the cause of her palpitations.
A stress echocardiogram combines ultrasound imaging of the heart before and after exercise with a standard treadmill ECG. It is a very reasonable test to order in a patient with palpitations and PVCs, as it allows us to assess for any significant problems with the heart muscle, valves or blood supply and to see if any more dangerous rhythms like ventricular tachycardia occur with exercise. If it is normal, we can state with high certainty that the PVCs are benign.
Benign, in this context, means the patient is not at increased risk of stroke, heart attack, or death due to the PVCs.
In the right hands, a stress echocardiogram is superior to a stress nuclear test for these kinds of assessments for three reasons:
-Reduced rate of false positives (test is called abnormal, but the coronary arteries have no significant blockages)
-No radiation involved (which adds to costs and cancer risk)
-The echocardiogram allows assessment of the entire anatomy of the heart, thus detecting any thickening (hypertrophy), enlargement or weakness of the heart muscle, that would mean the PVCs are potentially dangerous.
Unfortunately, my patient’s stress echo (done at another medical center) was botched and read as showing evidence for a blockage when there was none. An invasive and potentially life-threatening procedure, a cardiac catheterization was recommended. Similar to the situation I’ve pointed out with the performance and interpretation of echocardiograms (see here), there is no guarantee that your stress echo will be performed or interpreted by someone who actually knows what they are doing. So, although the stress echo in published studies or in the hands of someone who is truly expert in interpretation, has a low yield of false positives, in clinical practice the situation is not always the same.
Given that Janet was very active without any symptoms, she balked at getting the catheterization and came to me for a second opinion. I felt the stress echo was a false positive and did not feel the catheterization was warranted. We discussed alternatives, and because Janet needed more reassurance of the normality of her heart (partially because her father had died suddenly in his sixties) and thus the benignity of her palpitations/PVCs, she underwent a coronary CT angiogram instead. This noninvasive exam (which involves IV contrast administration, and is different from a coronary calcium scan), showed that her coronary arteries were totally normal.
Benign PVCs-Treatment Options
Once we have demonstrated that the heart is structurally normal, reassurance is often the only treatment that is needed. Now that the patient understands exactly what is going on with the heart and that it is common and not dangerous, they are less likely to become anxious when the PVCs come on.
PVCS can create a vicious cycle because the anxiety they provoke can cause an increase in neurohormonal factors (catecholamines/adrenalin) that may increase heart rate , make the heart beat stronger and increase the frequency of the PVCs.
Some patients, find their PVCs are triggered by caffeine (tea, soda, coffee, chocolate) or stress, and reducing or eliminating those triggers helps greatly. Others, like Janet, have already eliminated caffeine, and are not under significant stress.
Since I’m already over a thousand words in this post, I’ll discuss treatment options for these patients with benign PVCs who continue to have troubling symptoms after reassurance and caffeine reduction in a subsequent post.
The AliveCor/Kardia mobile ECG device is a really nifty way to monitor your heart rhythm. Since acquiring the third generation device (which sits within or on my iPhone case and communicates with a smartphone app) I have begun routinely using it on my patients who need a heart rhythm check during office visits. It saves us the time, inconvenience (shirt and bra removal) and expense of a full 12-lead ECG which I would normally use.
In addition, I’ve convinced several dozen of my patients to purchase one of these devices and they are using it regularly to monitor their heart rhythms. Typically, I recommend it to a patient who has had atrial fibrillation (Afib) in the past or who has intermittent spells of palpitations.
Some make daily recordings to verify that they are still in normal rhythm and others only make recordings when symptoms develop.
Once my email invitation request is accepted I can view the ECGs recorded by my patients who have AliveCor devices as I described here.
This monitoring has in many cases taken the place of expensive, obtrusive and clumsy long term event monitors.
In general, it has been very helpful but the device/app makes occasional mistakes which are significant and sometimes for certain patients it does a poor job of making a good recording.
Alivecor Success Stories
One of my patients, a spry ninety-something year young lady makes an AliveCor recording every day, since an episode of Afib 9 months ago.
And when I say every day I mean it literally everyday. It could be because she is compulsive or perhaps she has programmed the AliveCor to remind her. When I log in to the AliveCor site and click on her name I can see these daily recordings:
After a month of normal daily recordings, she suddenly began feeling very light headed and weak with a sensation that her heart was racing.
She grabbed her trusty iPhone and used the AliveCor device attached to it to make a recording of her cardiac rhythm. This time, unlike the dozens of other previous recordings, the device indicated her heart rate was 157 beats per minutes , about twice as fast as usual.
After 5 hours her symptoms abated and by the time of her next recording she had gone back to the normal rhythm.
She made two other recordings during the time she felt bad and they both confirmed Afib at rates of 140 to 150 beats per minute.
In this case, the device definitely alerted her to a marked and dramatic increase in heart rate but was not capable of identifying this as Afib In my experience with several hundred recordings, the device accurately identifies atrial fibrillation about 80% of the time. On rare occasions (see here) it has misidentified normal rhythm with extra beats as atrial fibrillation
AliveCor/kardia users have the option of having their recordings interpreted for a fee by a cardiologist or a technician.
My patients can alert me of a recording and I can go online and read the ECG myself and then contact the patient to inform them of my interpration of their heart rhythm and my recommendations.
Another patient made the recording below:Although she is at high risk of having a stroke during the times she is in Afib, we had been holding the blood thinner I had started her on because of bleeding from her mouth. I had instructed her to take daily recordings of her rhythm with the AliveCor until she was seen by her dentist to evaluate the bleeding.
In this case, the AliveCor performed appropriately, identifying correctly the presence of Afib which was the cause of her nocturnal symptoms.
A young woman emailed me that her AliveCor device on several occasions has identified her cardiac rhythm during times of a feeling of heart racing and palpitations as “possible atrial fibrillation.” When she sent the recordings in to AliveCor to have a paid interpretation, however, the recordings were interpreted as sinus tachycardia with extra beats. Indeed , upon my review her rhythm was not Afib. Clearly, when the device misidentifies Afib, this has the potential for creating unnecessary anxiety.
It is not uncommon for a full, 12-lead ECG done in the hospital or doctor’s office by complex computer algorithms to misinterpret normal rhythm as Afib so I’m not surprised that this happens with AliveCor using a single lead recorded from the fingers.
The young woman was advised by AliveCor to try a few things such as using the device in airplane mode, sitting still and wetting her fingers which did not help. She was sent a new device and the problem persisted. She finds that putting the device on her chest gives a better chance of success.
She also runs into a problem I see frequently which is a totally normal recording labeled by the device as “unclassified.”
In this example, although I can clearly see the p-waves indicating normal sinus rhythm, the voltage is too low for the device to recognize.
Send Me Your AliveCor Problems and Solutions
I’m interested in collecting more AliveCor/Kardia success and failure stories so please post yours in the comments or email me directly at DRP@theskeptical cardiologist.com.
In addition, I’m interested in any tips AliveCor users have to enhance the success of their recordings: What techniques do you use to make the signal strength and recording better? What situations have you found that tend to worsen the signal strength and recording quality?
Still Unclassified Yours,
P.S. Tomorrow is Cyber Monday and I note that Kardia is running a “Black Friday” special through 11/28, offering the device at 25% off.
P.P.S. Kardia, You should change the statement on your website, “90% of strokes are preventable if you catch the symptoms early.” makes no sense. I think you mean that some strokes are preventable (I have no idea where the 90% figure come from) if one can detect Afib by utilizing a monitoring device to assess symptoms such as palpitations or irregular heart beat.
As December draws ever closer to the twenty-fifth you may find yourself behind the wheel of a large automobile puzzling over the perfect gift for your loved ones.
Fear not, for the skeptical cardiologist has a few suggestions to help you.
The Omron 10 Blood Pressure Monitor
If your hypertensive friend or relative already has all the standard BP paraphernalia (pill splitter, basic BP cuff), owns a smart phone and has an engineer or scientist approach to data the Omron 10 (BP786, 59.99$ at Best buy.com) just might be the perfect gift.
The skeptical cardiologist recently purchased two (that’s right two) of these in anticipation of Christmas.
Christmas arrives with multiple stressors guaranteed to hike your blood pressure.
The Omron 10 offered three features not available on my basic Walgreen’s BP cuff that I felt were possibly useful:
Averaging/automating three consecutive readings. After reading about the SPRINT BP trial which showed a benefit of aiming for SBP of 120 over 140, I thought I should try to reproduce the method used in the trial. This involved measuring BP 3 times separated by 5 minutes and averaging the results. The Omron 10 can be set to make and average three BP readings separated by a variable time period.
The ability to communicate with an iPhone or Android smartphone and record and display the data in an app.
Works off both batteries and plug in electrical power.
I thought my dad (a retired chemist) would like the Omron 10’s features but, alas, he informed me that if he wanted to average three BP readings he could just write down the numbers and do the math.
If he had an iPhone he might really like the way the Omron sends its data to the free Omron app.
The app displays BP and heart rate readings recorded for different time intervals.
You can take a screen shot like I did here or email it and share the data with your doctor through the doctor’s patient portal!
I’ve mentioned this really cool device a few times (here and here).
It is now listed on Amazon.com for $57 (a significant drop from when I purchased it) and can be attached to your smartphone case. It does a really good job of recording a single lead electrocardiogram (ECG) and diagnosing normality or atrial fibrillation.
If your friend or loved one is experiencing periodic fluttering in their chest or a sensation of the heart skipping beats or racing (the general term for which is palpitations) then this could be the perfect gift.
A number of my patients have purchased these and have made ECG recordings which I can review online.
Primarily I have been recommending them to my patients who have atrial fibrillation periodically.
You may think this is too complicated a device to master but last week I saw in my office a 94 year old lady who had had an episode of atrial fibrillation earlier in the year. Since her last visit she had purchased an AliveCor device and was able to show me the ECG recordings she had made on her iPhone.
May your holiday season be joyous, full of loved ones and free of stressors that raise your blood pressure and cause your heart to pound and race. But if it is not, consider purchasing one of these nifty devices.
The skeptical cardiologist has been evaluating the AliveCor mobile ECG device for use with a smartphone to detect atrial fibrillation. In my initial post on this I found it to be accurate in identifying atrial fibrillation in my patients.
I’ve been using it in my office fairly regularly and encouraging my patients with intermittent AF to acquire the device and use it to monitor their heart rhythm.
When they make recordings they can be uploaded to me via internet for my review.
The other day I was examining a patient who I was seeing for syncope (passing out) and I noticed when listening to his heart that his pulse was very irregular.
I pulled out my iPhone with AliveCor stuck on the case and made the recording you see below.
Although the AliveCor app diagnosed it as “possible AF” it is very clearly normal sinus rhythm with frequent premature ventricular contractions (PVC), a totally different (and more benign) rhythm.
I’ll continue on with this evaluation and I’ll be particularly interested in how AliveCor performs in other patients with PVCs which are a common cause of palpitations in the general population.
If AliveCor cannot differentiate AF from PVCS it may lead a lot of users to become unduly concerned about their heart rhythm.