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.
The skeptical cardiologist has been a huge advocate of personal mobile ECG monitoring to empower patient’s in understanding/monitoring their heart rhythm.
The deserved leaders in this field are the Apple Watch (4 and later) and Alivecor’s Kardia device which comes in single-lead and six-lead flavors.
Both Apple and AliveCor have gotten FDA approval for their mobile ECG device and have a body of published studies supporting their accuracy.
In contrast, there are a number of “copy-cat” mobile ECG devices which have been feeding on the success of Apple Watch and Kardia but do not have the bona fides the two leaders have.
I reviewed the SonoHealth ECG here and found it sorely lacking in comparison to Kardia in terms of accuracy of diagnosis and quality of recordings, the two most important aspects of a personal ECG monitor.
Dan Field, a physician and reader of my blog, has been evaluating a device similar to the SonoHealth ECG made by Emay.
He has provided a point by point comparison of the two devices in the chart below
“The Kardia6L was clearly superior in almost every way except for price and even that was within the margin of error. ”
It should be noted that the single lead Kardia mobile ECG is actually cheaper than the Emay and retails for $99.
Let The (Mobile ECG) Buyer Beware
I ended my post reviewing SonoHealth’s ECG with a warning which applies equally to the Emay device:
The SonoHealth EKGraph is capable of making a reasonable quality single lead ECG. Presumably all the other devices utilizing the same hardware will work as well.
However, the utility of these devices for consumers and patients lies in the ability of the software algorithms to provide accurate diagnoses of the cardiac rhythm.
Apple Watch 4 and AliveCor’s Kardia mobile ECG do a very good job of sorting out atrial fibrillation from normal rhythm but the SonoHealth EKGraph does a horrible job and should not be relied on for this purpose.
The companies making and selling the EKGraph and similar devices have not done the due diligence Apple and AliveCor have done in making sure their mobile ECG devices are accurate. As far as I can tell this is just an attempt to fool naive patients and consumers by a combination of marketing misinformation and manipulation.
I cannot recommend SonoHealth’s EKGraph or any of the other copycat mobile ECG devices. For a few dollars more consumers can have a proven, reliable mobile ECG device with a solid algorithm for rhythm diagnosis. The monthly subscription fee that AliveCor offers as an option allows permanent storage in the cloud along with the capability to connect via KardiaPro with a physician and is well worth the dollars spent.
I can’t vouch for the Keyto chocolate shake or the basil pesto that they are now including with Black Friday sales but I love the Keyto.
By the way, it wasn’t clear to me when I first got the Keyto device what kind of diet Keyto promotes. They favor a plant-based keto (with fish) diet which they consider “heart healthy.” More on this down the line.
One of the joys of writing this blog is the communication it allows me with discerning individuals and patients across the planet. One such reader, Mark Goldstein, discovered he was in atrial fibrillation after purchasing an Apple Watch 4.
He now utilizes both the Kardia Mobile ECG and the Apple Watch to aid in his personal monitoring of his atrial fibrillation and has been actively pursuing a rhythm control strategy under the care of his electrophysiologist.
I asked him to share with my readers his experience which recently culminated in an ablation.
What follows is his description with my editorial comments in green.
December 2018 I bought a crazy, expensive Apple Watch. That watch may have saved my life. I spend much of my days at a treaddesk (a combination desk and treadmill). I was curious to find out how much exercise I was doing. I bought the watch, put it on, and starting walking as I do almost every day. Two hours later the watch had an alarm. It was warning me about something called “atrial fibrillation,” It said, “your heart has shown signs of an irregular rhythm.” What! I never heard of afib before. I quickly learned about it. Heart palpitations, no. Pain/pressure in the chest, no. Sweaty, faint, dizzy, etc., no, no. no. I checked the box for tired but I assumed it was because of the amount of exercise I was doing.
The next day I was fortunate that I had a physical scheduled a year ago. I told my doctor that my “crazy, expensive watch” thinks I have afib. My doctor laughed, telling me about how he had checked and probed every part of my body for the last 20 years (the probing part I remembered well). As the exam was concluding, he was puzzled by the afib warning so he grabbed my wrist to check my pulse. A few seconds later he was asking the nurse to give me an EKG. Darn, the watch was correct (and for me it was correct 99% of the time when I had afib and when I was normal – praise to Apple).
(This is a great example of how atrial fibrillation can be missed by the routine office physical examination. Some patients, especially those with non-rapid heart rates (due to rate slowing meds like beta-blockers or to intrinsically slow conduction of electrical impulses) are minimally symptomatic and their pulses don’t feel that irregular. Because the first symptom of afib can be stroke I am an advocate of screening)
Shortly I got to meet a cardiologist (like Dr. Pearson, they are all nice people). Another EKG, afib confirmed. As we were talking about my symptoms or lack of symptoms, he said that afib was a bit like Eskimo’s describing snow. Each snowflake is unique and each afib patient is unique. I was in persistent afib. Probably had been in this state for two or three years since my heart rate jumped while sleeping, exercising, and at rest.
(Each afib experience is unique but not all cardiologists are nice people. Mark has been fortunate.)
The treatment plan was a cardioversion, an electrical shock to the heart, or as my cardiologist described it “like rebooting a computer.”
As a tech person, I understood that. The risk of not fixing my afib was five times the likelihood of a stroke. The risks were minimal so I chose the cardioversion.
(A common misconception is that ablation or cardioversion eliminates or substantially lowers the risk of stroke in afib. This is not the case. I’ll devote a future post to delve into this issue.)
Cardioversion one lasted four days before my Apple Watch started to detect afib.
(I’ve described in detail how helpful patient utilization of personal ECG monitoring is in letting me know the rhythm status of patients prior to and following cardioversion here.)
The cardiologist next step was cardioversion two along with a drug to help with rhythm control. Number two lasted a month before I saw my heart rate jump again. I thought something was wrong even though my watch was not detecting afib. Another EKG, this time the result was aflutter. The cardioversions were indeed like a reboot of the computer. If you have a virus on your computer, a reboot may be a temporary fix but eventually the virus will return.
(There are many drugs whose purpose is to suppress the recurrence of atrial fibrillation. Mark was prescribed the extended release version of propafenone, a Type IC antiarrhythmic drug (AAD) similar in efficacy and side effects to flecainide. Type IC AADs should only be used in patients with normal left ventricular function (which was demonstrated in Mark by an echo) and without significant coronary artery disease (typically proven by a negative stress test).
To Ablate Or Not To Ablate
Now I got to meet an electrocardiologist. He said my afib would return and recommended an ablation. He said it was unlikely to be a permanent cure but it would help.
The aflutter disappeared after a day or so. I thought my afib was gone too but should I have an ablation? Ablations are relatively safe but since I was afib free why have the procedure?
I purchased the new Kardia Mobile six-lead portable EKG, a miracle of technology. Highly recommended for peace of mind. Just like my watch, I was seeing normal sinus rhythm. So why get an ablation?
A cardiologist had a YouTube video talking about the decision to have an ablation or any medical procedure. How will it affect the quality of your life or the quantity (how long will you live). This was a simple analysis and I like simple. I heard from my cardiologist that the evidence is that an ablation will unlikely extend my life nor will it reduce my lifespan. It was likely to not affect my lifespan. I confirmed this via independent research (be an informed patient, your outcomes will be better). See Dr Pearson’s articles about the CABANA study and the scientific evidence on ablation). So an ablation and quantity of life were neutral.
Importance Of Quality Of Life
Quality of life was more interesting. Could I do the things wanted to do with my life? Did afib affect my day-to-day life? Could I walk up a couple of flights of stairs without breathing hard? Was I getting tired at 10AM? Could I exercise? At the time, the answer was easy. I could do everything I wanted to do. The afib affect was just about zero except for blood thinner drugs which I suspect I will take forever. No ablation.
Then “the day.” I woke and checked my sleep app on my phone. Heart rate at night jumped. Hmm! I went to the gym. My heart rate while walking jumped too. I did 30 seconds of high-intensity exercise and my heart rate monitor said 205 beats per minute. My heart was beating so hard I had to sit for five minutes. I knew something was wrong. Then I climbed a couple of flights of stairs, something that would never bother me. I felt a shortness of breath. I knew my afib was back. I also knew that the quality of my life was now being affected. I could not do things I wanted to do. My watch and Kardia Mobile EKG confirmed what I knew.
I called my electrocardiologist and scheduled an ablation. He was right. Afib would return.
(Mark tells me that he was taken off his propafenone one month after the second cardioversion because “the PA said I no longer needed it since I was in sinus rhythm.” My practice would have been to continue the propafenone as long as well tolerated and effective in suppressing afib recurrence. In my experience, the recurrence of Mark’s afib may not have been a failure of medical therapy. I treat patients similar to Mark by continuing the anti-arrhythmic drug since the minimal risks are lowered by regular monitoring and I regularly see maintenance of SR.”)
(Other antiarrhythmic medications were mentioned to Mark but as they required a 3 day hospital stay he was not interested.)
Stay tuned: Part two Of Mark’s post will be about the ablation procedure which he recently underwent.
The skeptical cardiologist still feels that KardiaPro has eliminated use of long term monitoring devices for most of his afib patients
However not all my afib patients are willing and able to self-monitor their atrial fibrillation using the Alivecor Mobile ECG device. For the Kardia unwilling and many patients who don’t have afib we are still utilizing lots of long term monitors.
The ambulatory ECG monitoring world is very confusing and ever-changing but I recently came across a nice review of the area in the Cleveland Clinic Journal of Medicine which can be read in its entirety for free here.
This Table summarizes the various options available. I particularly like that they included relative cost. .
The traditional ambulatory ECG device is the “Holter” monitor which is named after its inventor and is relatively inexpensive and worn for 24 to 48 hours.
The variety of available devices are depicted in this nice graphic:
For the last few years we have predominantly been using the two week “patch” type devices in most of our patients who warrant a long term monitor. The Zio is the prototype for this but we are also using the BioTelemetry patch increasingly.
The more expensive mobile cardiac outpatient telemetry (MCOT) devices like the one below from BioTel look a lot like the patches now. The major difference to the patient is that the monitor has to be taken out and recharged every 5 days. In addition, as BioTel techs are reviewing the signal from the device they can notify the patient if the ECG from the patch is inadequate and have them switch to an included lanyard/electrode set-up.
The advantage of the patch monitors is that they are ultraportable, relatively unobtrusive and they monitor continuously with full disclosure.
The patch is applied to the left chest and usually stays there for two weeks (and yes, patients do get to shower during that time) at which time it is mailed back to the company for analysis.
The skeptical cardiologist was quite enthusiastic about AliveCor’s Kardia Band for Apple Watch upon its release late in 2017.
I was able to easily make high fidelity, medical grade ECG recordings with it and its AI algorithm was highly accurate at identifying atrial fibrillation (see here). This accuracy was subsequently confirmed by research.
Many skepcard readers spent $200 dollars for the Kardia Band and had found it to be very helpful in the management of their atrial fibrillation.
However, in December of 2018 Apple added ECG recording to its Apple Watch 4, essentially building into the AW4 the features that Kardia Band had offered as an add on to earlier Apple Watch versions.
In my evaluation of the Apple Watch I found it to be “an amazingly easy, convenient and straightforward method for recording a single channel ECG” but its algorithm in comparison to AliveCor’s yielded more uncertain diagnoses.
Given it size, prominence and vast resources, Apple’s very publicized move into this area seemed likely to threaten the viability of AliveCor’s Kardia Band.
But then-interim CEO (and current COO) Ira Bahr later told MobiHealthNews that his company’s broader business wasn’t threatened by its new direct competitor.
“We’re not convinced that Apple’s excellent, engaging product is a competitor yet,” he said in February. “We believe that from a price perspective, this product is least accessible to the people who need it most. If you’re not an Apple user, you’ve got to buy an Apple Watch, you’ve got to buy an iPhone to make the system work. So their technology is excellent, but we think the platform is both complicated and expensive and certainly not, from a marketing perspective, targeting the patient populations we target.”
Indeed, AliveCor’s Mobile ECG device and its recently released 6 lead ECG are doing very well but the threat to the viability of KardiaBand was real and MobiHealth News announced Aug. 19 that AliveCor had officially ended sales of the Kardia Band.
An AliveCor representative told MobiHealthNews that the company “plans to continue supporting KardiaBand indefinitely” for those who have already purchased the device. The company’s decision was first highlighted by former MobiHealthNews Editor Brian Dolan in an Exits and Outcomes report.
Mr. Bahr has confirmed to me that AliveCor does plan to continue supporting KardiaBand indefinitely. This includes replacement of KardiaBand parts.
Did Apple Kill Smart Rhythm?
The informed reader who notified me of AliveCor’s decision also notes:
The official reason is that they could not keep up with the Apple Watch updates and therefore the Smart Rhythm feature did not work properly.
I think many of us knew from the beginning that smart rhythm was not very accurate But in spite of that the Kardia band provided a valuable convenience over their other products.
It does appear that Smart Rhythm is no more.
AliveCor’s website was updated 6 days ago to state that Smart Rhythm was discontinued:
” due to changes beyond our control in the Apple Watch operating system, which caused SmartRhythm to perform below our quality standards”
Likely, as my reader was told, the frequent AW4 updates plus the lack of a large KardiaBand user base made it unprofitable for AliveCor to continue to support Smart Rhythm.
Smart Rhythm, of course was AliveCor’s method for watch-based detection of atrial fibrillation. It clearly had limitations, including false positives but given AliveCor’s track record of dedication to high quality and accuracy I assumed it would improve over time..
Apple, on December 6, 2018 with the release of its watchOS 5.1.2 for AW4 announced its own version of Smart Rhythm at the same time it activated the ECG capability of AW4.
Apple called this feature “the irregular rhythm notification feature” and cited support for its accuracy from the widely ballyhooed Apple Heart Study (which I critiqued here.)
The irregular rhythm notification feature (TIRNF)was recently studied in the Apple Heart Study. With over 400,000 participants, the Apple Heart Study was the largest screening study on atrial fibrillation ever conducted, also making it one of the largest cardiovascular trials to date. A subset of the data from the Apple Heart Study was submitted to the FDA to support clearance of the irregular rhythm notification feature. In that sub-study, of the participants that received an irregular rhythm notification on their Apple Watch while simultaneously wearing an ECG patch, 80 percent showed AFib on the ECG patch and 98 percent showed AFib or other clinically relevant arrhythmias.
Despite widely publicized reports of lives being saved by TIRNF we still don’t know whether its benefits outweigh its harms. It is not clear what its sensitivity is for detecting atrial fibrillation and I have reported one patient who was in atrial fibrillation for 3 hours without her AW4 alerting her to its presence.
For AW4 users, absence of an alert should not provide reassurance that your rhythm is normal.
Thus is does appear that the Goliath Apple hath smote the David AliveCor in the watch-based afib battle. This does not bode well for consumers and patients as I think as competition in this area would make for better products and more accountability.
Per AliveCor the KardiaBand currently works with all all Apple Watches except the original one.
The Apple TIRNF per Apple:
is available for Apple Watch Series 1 and later and requires iPhone 5s or later on iOS 12.1.1 in the US, Puerto Rico, Guam and US Virgin Islands. The irregular rhythm notification feature does not detect a heart attack, blood clots, a stroke or other heart-related conditions including high blood pressure, congestive heart failure, high cholesterol or other forms of arrhythmia.
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.
Many patients (and perhaps physicians) are confused as to how best to utilize personal ECG devices. I received this question illustrating such confusion from a reader recently:
I first came across your website a year ago during persistent angina attacks, and returning now due to increasing episodes of symptoms akin to Afib. I bought a Kardia 2 yrs ago for the angina episodes, and looking to buy the Apple Series 4 for the Afib, as I want to try a wearable for more constant monitoring. What I would greatly appreciate if you had a basic guide for both the Kardia & Apple devices, specifically when and how to best employ them for unstable angina and detecting undiagnosed Afib. As in, what can I as a patient provide to you as a doctor for diagnosis in advance of a formal visit. I’m a US Iraq vet medically retired in the UK, and most of my concerns get dismissed out of hand as “anxiety”, not sure why they thought a stent would cure my anxiety though
First. please understand that none of these devices have any significant role in the management of angina. Angina, which is chest/arm/jaw discomfort due to a poor blood supply to the heart muscle cannot be reliably diagnosed by the single lead ECG recording provided by the Apple Watch, the Kardia Band or the Kardia mobile ECG device. Even a medical-grade 12 lead ECG doesn’t reliably diagnose angina and we rely on a constellation of factors from the patient’s history to advanced testing to determine how best to manage and diagnose angina.
Second, as you are having episodes “akin to Afib”, all of these devices can be helpful in determining what your cardiac rhythm is at the time of the episodes if they last long enough for you to make an ECG recording.
The single lead ECG recording you can make from the Apple Watch, the Kardia Band and from the Kardia mobile device can very reliably tell us what the cardiac rhythm was when you were feeling symptoms.
The algorithms of these devices do a good job of determining if the rhythm Is atrial fibrillation. Also, if the rhythm is totally normal they are good at determining normality.
These tracings can be reviewed by a competent cardiologist to sort out what the rhythm really is.
In all of these cases, having an actual recording of the cardiac rhythm at the time of symptoms is immensely helpful to your doctor or cardiologist in determining what is causing your problems.
My recommendation, therefore, would be to make several recordings at the time of your symptoms. Print them out and carefully label the print-out with exactly what you were feeling when it was recorded and present these to the doctor who will be reviewing your case.
As I’ve mentioned in previous posts (see here), my patients’ use of Kardia with the KardiaPro online service has in many cases taken the place of expensive and inconvenient long term monitoring devices.
Case Example-Diagnosing Rare And Brief Attacks Of Atrial Fibrillation
I recently saw a patient who I think perfectly demonstrates how useful these devices can be for clarifying what is causing intermittent episodes of palpitations-irregular, pounding, or racing heart beats.
She was lying on a sofa one day when she suddenly noted her heart “pumping fast” and with irregularity. The symptoms last for about an hour. She had noticed this occurred about once a year occurring out of the blue.
Her PCP ordered a long term monitor, a stress test and an echocardiogram.
The monitor showed some brief episodes of what I would term atrial tachycardia but not atrial fibrillation but the patient did not experience one of her once per year hour long episodes of racing heart during the recording. Thus, we had not yet solved the mystery of the prolonged bouts of racing heart.
She was referred to me for evaluation and I recommended she purchase an Alivecor device and sign up for the KardiaPro service which allows me to view all of her recordings online. The combination of the device plus one year of the KardiaPro service costs $120.
She purchased the device and made some occasional recordings when she felt fine and we documented that these were identified as normal by Kardia. For months nothing else happened.
Then one day in April she had her typical prolonged symptom of a racing heart and she made the recording below (She was actually away from home but had the Kardia device with her.)
When she called the office I logged into my KardiaPro account and pulled up her recordings and lo and behold the Kardia device was correct and she was in atrial fibrillation at a rate of 113 BPM.
With the puzzle of her palpitations solved we could now address proper treatment.
Continuous Monitoring for Abnormal Rhythms
Finally, let’s discuss the wearables ability to serve as a monitor and alert a patient when they are in an abnormal rhythm but free of any symptoms.
My reader’s intent was to acquire a device for “constant monitoring”:
I’m looking to buy the Apple Series 4 for the Afib, as I want to try a wearable for more constant monitoring.
This capability is theoretically available with Apple Watch 4’s ECG and with the Kardia Band (using SmartRhythm) which works with Apple Watch Series 1-3.
However, I have not been impressed with Apple Watch’s accuracy in this area (see here and here) and would not at this point rely solely on any device to reliably alert patients to silent or asymptomatic atrial fibrillation.
In theory, all wearables that track heart rate and alert the wearer if the resting heart rates goes above 100 BPM have the capability of detecting atrial fibrillation. If you receive an alert of high HR from a non ECG-capable wearable you can then record an ECG with the Kardia mobile ECG to see if it really is atrial fibrillation.
At 99$, the Kardia is the most cost-effective way of confirming atrial fibrillation for consumers.
I hope this post adds some clarity to the often confusing field of personal and wearable ECG devices.
The skeptical cardiologist recently received this email from a reader:
With the new Apple Watch that’s out now, people have suggested my husband (who had a heart attack at 36) should get it since it could detect a heart attack. But I keep remembering what you said – that these devices can’t detect heart attacks and that Afib isn’t related to a heart attack most of the time – is that still the case? I don’t really know how to explain to people that it can’t do this, since absolutely everyone believes it does.
The answer is a resounding and unequivocal NO!
If we are using the term heart attack to mean what doctors call a myocardial infarction (MI) there should be no expectation that any wearable or consumer ECG product can reliably diagnose a heart attack.
The Apple Watch even in its latest incarnation and with the ECG feature and with rhythm monitoring activated is incapable of detecting a myocardial infarction.
To make this even clearer note that when you record an ECG on the Apple Watch it intermittently flashes the following warning:
Note: “Apple Watch never checks for heart attacks”
How did such this idea take root in the consciousness of so many Americans?
Perhaps this article in 9-5 Mac had something to do with it
In reality, the man received an alarm that his resting heart rate was high at night. Apparently he also was experiencing chest pain and went to an ER where a cardiac enzyme was elevated. Subsequently he underwent testing that revealed advanced coronary artery disease and he had a bypass operation.
Even if we assume all the details of this story are accurate it is absolutely not a case of Apple Watch diagnosing an MI.
A high resting heart rate is not neccessarily an indicator of an MI and most MIs are not characterized by high heart rates. We have had the technology with wearables to monitor resting heart rate for some time and no one has ever suggested this can be used to detect MI.
The rate of false alarms is so high and the rate of failure to diagnose MI so low that this is a useless measure and should not provide any patient reassurance.
The writer of this story and the editors at 9-5 Mac should be ashamed of this misinformation.
Several other news sources have needlessly muddied the water on this question including Healthline and Fox News:
In clear cut cases the Apple Watch could make the difference between life and death,” says Roger Kay, president of Endpoint Technologies Associates. Because you wear the Apple Watch at all times, it can detect an early sign of a stroke or a heart attack, and that early indication is critical, he says.
And the Healthline article on the new Apple Watch also incorrectly implies it can diagnose MI:
The device, which was unveiled last week, has an electrocardiogram (ECG) app that can detect often overlooked heart abnormalities that could lead to a heart attack.
And if you are felled by a heart problem, the fall detector built into the Apple Watch Series 4 could alert medical professionals that you need help
Fox News and Healthline should modify their published articles to correct the misinformation they have previously provided.
And it is still true that although both Apple Watch and Kardia can diagnose atrial fibrillation the vast majority of the time acute heart attacks are not associated with atrial fibrillation.
Readers, please spread the word far and wide to friends and family-Apple Watch cannot detect heart attacks!
My first patient this morning, a delightful tech-savvy septagenarian with persistent atrial fibrillation told me she had been monitoring her rhythm for the last few days using her Apple Watch 4’s built in ECG device.
I had been eagerly awaiting Apple’s roll out since I purchased the AW4 in September (see here) and between patients this morning I down-loaded and installed the required iPhone and Watch upgrades and began making AW4 recordings.
Through the day I tried the AW4 and the Kardia on patients in my office.
Apple Watch 4 ECG Is Easy and Straightforward
The AW4 ECG recording process is very easy and straightforward. Upon opening the watch app you are prompted to open the health app on your iPhone to allow connection to the Watch ECG information. After this, to initiate a recording simply open the Watch ECG app and hold your finger on the crown.
Immediately a red ECG tracing begins along with a 30 second countdown.
Helpful advice to pass the time appears below the timer:
“Try Not to move your arms.”
“Apple Watch never checks for heart attacks.”
When finished you will see what I and my patient (who mostly stays in sinus rhythm with the aid of flecainide) saw-a declaration of normality:
Later in the day I had a few patients with permanent atrial fibrillation put on my watch.
This seventy-something farmer from Bowling Green, Missouri was easily able to make a very good ECG recording with minimal instruction
The AW4 nailed the diagnosis as atrial fibrillation.
We also recorded a Kardia device ECG on him and with a little more instruction the device also diagnosed atrial fibrillation
After you’ve made an AW4 recording you can view the PDF of the ECG in the Health app on your iPhone where all of your ECGs are stored. The PDF can be exported to email (to your doctor) or other apps.
Apple Watch Often “Inconclusive”
The AW4 could not diagnose another patient with permanent atrial fibrillation and judged the recording “inconclusive”
The Kardia device and algorithm despite a fairly noisy tracing was able to correctly diagnose atrial fibrillation in this same patient.
I put the AW4 on Sandy, our outstanding echo tech at Winghaven who is known to have a left bundle branch block but remains in normal rhythm and obtained this inconclusive report .
Kardia, on the other hand got the diagnosis correctly:
One Bizarre Tracing by the AW4
In another patient , an 87 year old lady with a totally normal recording by the Kardia device, the AW4 yielded a bizarre tracing which resembled ventricular tachycardia:
Despite adjustments to her finger position and watch position, I could not obtain a reasonble tracing with the AW4.
The Kardia tracing is fine, no artifact whatsoever.
What can we conclude after today’s adventures with the Apple Watch ECG?
This is an amazingly easy, convenient and straightforward method for recording a single channel ECG.
I love the idea that I can record an ECG whereverI am with minimal fuss. Since I wear my AW4 almost all the time I don’t have to think about bringing a device with me (although for a while I had the Kardia attached to iPhone case that ultimately became cumbersome.)
Based on my limited sample size today, however, the AW4 has a high rate of being uncertain about diagnoses. Only 2/3 cases of permanent atrial fibrillation were identified (compared to 3/3 for the Kardia) and only 4/6 cases of sinus rhythm were identified.
If those numbers hold up with larger numbers, the AW4 is inferior to the Kardia ECG device.
I’d rather see the AW4 declare inconclusive than to declare atrial fibrillation when it’s not present but this lack of certainty detracts from its value.
What caused the bizarre artifact and inconclusive AW4 tracing in my patient is unclear. If anybody has an answer, let me know.
We definitely need more data and more studies on the overall sensitivity and specificity of the AW4 and hopefully these will be rapidly forthcoming.
For most of my patients the advantages of the AW4 (assuming they don’t already have one) will be outweighed by its much greater cost and we will continue to primarily utilize the Kardia device which will also allow me to view all of their recordings instantaneously in the cloud.
Note. The original version of this post had the wrong ECG tracing for the first “inconclusive” AW4 recording of a patient with permanent atrial fibrillation. H/t to discerning reader Vignesh for pointing this out months after the initial posting.