Atrial Fibrillation

Kardia Mobile EKG

Atrial fibrillation (AF) is a common abnormal heart rhythm. The prevalence of AF ranges from 0.1 percent of adults less than 55 years of age to 9 percent in those above 80.[1] In the Framingham Heart Study the risk of developing AF from age 40 to age 95 was 26 percent for men and 23 percent for women.[2] Atrial fibrillation may be intermittent (paroxysmal) or continuous. It may be asymptomatic or cause significant symptoms such as palpitations, chest pain, shortness of breath, fatigue, and dizziness. AF is associated with hypertension, coronary heart disease, heart failure, valvular heart disease, alcohol excess, and hyperthyroidism.

AF occurs when the atria of the heart (upper chambers) stop contracting normally resulting in irregular and usually rapid contractions of the ventricles (lower chambers). This may cause impaired exercise tolerance, low cardiac output, and heart failure. Also, blood clots may form in the atria, break loose, and travel to the brain resulting in a stroke. The risk of stroke increases five fold with AF.

Thus, AF is common and although often intermittent and asymptomatic, it nevertheless increases the risk of stroke. In 2018 the US Preventative Services Task Force considered whether screening for AF with an EKG should be performed in asymptomatic people.[3] They balanced the benefit of treating asymptomatic AF against the risks of additional diagnostic testing and treatment. They found that systematic screening with ECG identified more cases of AF than no screening (absolute increase from 0.6 to 2.8 percent over 12 months). Systematic screening with ECG did not detect more cases than a systematic approach using pulse palpation (two trials and 17,803 patients).They concluded that “that the current evidence is insufficient to assess the balance of benefits and harms of screening for atrial fibrillation with ECG”.This recommendation will be updated this year.

Nevertheless, many people with a history of cardiac arrhythmias and /or palpitations would like to have rapid access to an electrocardiogram when experiencing symptoms, and be able to send the results to their medical care provider for diagnosis and possible treatment. Such wearable and home devices are now available from several equipment manufacturers. A recent international survey of healthcare professionals found that “57% … advise wearable/apps for atrial fibrillation detection” particulary for elderly (>65 years) and patients with risk factors for AF. However, “70% of healthcare professional believe we are not ready for mass consumer-initiated AF screening.”[4]

The mSTloPS Randomized Clinical Trial monitored 2659 at high risk for AF individuals with a wearable ECG sensor patch randomized to immediate home-based or delayed by four months. “Monitored indivuiduals, compared with nonmonitored controls, had higher rates of AF diagnosis, greater initiation of anticoagulants, but also increased health care resoure utilization at 1 year”.[5]

KardiaMobile is an “FDA-cleared, clinical grade personal EKG monitor. Kardia captures a medical-grade EKG in 30 seconds anywhere, anytime.”[6] KardiaMobile connects with a cell phone, and the interpreted EKG can be emailed to oneself or to a medical care provider. Recently Kardia has developed a new version of the monitor that can record 6 leads instead of just one and thus provide more information to the physician. This of course is stlll less than a standard 12-lead EKG. According to the Kardia website “KardiaMobile 6L is not tested or recommended for use with pacemakers and ICDs. KardiaMobile 6L does not check for heart attack.”

The AliveCor FDA Indications for Use Statement 510(k) states:[7]

Kardia Mobile (previously AliveCor Heart Monitor) is intended to record, store, and transfer single-channel electrocardiogram (ECG) rhythms. Kardia Mobile also displays ECG rhythms and detects the presence of atrial fibrillation and normal sinus rhythm (when prescribed or used under the care of a physician).

Kardia Mobile is intended for use by healthcare professionals, patients with known or suspected heart conditions, and health-conscious individuals. The product has not been tested and it is not intended for pediatric use.

Clinical studies have evaluated Kardia Mobile. Halcox et al:[8]

…conducted a randomized controlled trial of AF screening using an AliveCor Kardia monitor attached to a WiFi-enabled iPod to obtain ECGs (iECGs) in ambulatory patients. Patients ≥65 years of age with a CHADS-VASc score ≥2 free from AF were randomized to the iECG arm or routine care (RC). iECG participants acquired iECGs twice weekly over 12 months… They concluded:

Screening with twice-weekly single-lead iECG with remote interpretation in ambulatory patients ≥65 years of age at increased risk of stroke is significantly more likely to identify incident AF than RC [routine care] over a 12-month period. This approach is also highly acceptable to this group of patients, supporting further evaluation in an appropriately powered, event-driven clinical trial.

In the iRead Study, Kanbour et al assessed the accuracy of Kardia Mobile recordings:[9] Serial 12-lead electrocardiograms (ECGs) and nearly simultaneously acquired KMCM [Karia Mobile Cardiac Monitor] recordings were obtained.

RESULTS There were 225 nearly simultaneously acquired KMCM and ECG recordings across 52 enrolled patients (mean age 68 years; 67% male). After exclusion of unclassified recordings, the KMCM automated algorithm interpretation had 96.6% sensitivity and 94.1% specificity for AF detection as compared with physician interpreted ECGs, with a k coefficient of 0.89. Physician interpreted KMCM recordings had 100% sensitivity and 89.2% specificity for AF detection as compared with physician-interpreted ECGs, with a k coefficient of 0.85. Sixty-two recordings (27.6%) were unclassified by the KMCM algorithm. In these instances, physician interpretation of KMCM recordings had 100% sensitivity and 79.5% specificity for AF detection as compared with 12-lead ECG interpretation, with a k coefficient of 0.71.

CONCLUSION The KMCM system provides sensitive and specific AF detection relative to 12-lead ECGs when an automated interpretation is provided. Direct physician review of KMCM recordings can enhance diagnostic yield, especially for unclassified recordings.

The Apple Watch now also has the capability to do single lead EKG and to monitor pulse rate and rhythm. FDA cleared the device for marketing with the following indications for use:[10]

The ECG app is a software-only mobile medical application intended for use with the Apple Watch to create, record, store, transfer, and display a single channel electrocardiogram (ECG) similar to a Lead I ECG. The ECG app determines the presence of atrial fibrillation (AFib) or sinus rhythm on a classifiable waveform. The ECG app is not recommended for users with other known arrhythmias. The ECG app is intended for over-the-counter (OTC) use. The ECG data displayed by the ECG app is intended for informational use only. The user is not intended to interpret or take clinical action based on the device output without consultation of a qualified healthcare professional. The ECG waveform is meant to supplement rhythm classification for the purposes of discriminating AFib from normal sinus rhythm and not intended to replace traditional methods of diagnosis or treatment. The ECG app is not intended for use by people under 22 years old.

Furthermore, the FDA classified the device as:

Electrocardiograph software for over-the-counter use. An electrocardiograph software device for over-the-counter use creates, analyzes, and displays electrocardiograph data, and can provide information for identifying cardiac arrhythmias. This device is not intended to provide a diagnosis.

The FDA released a statement in 2018 regarding the Apple Watch:[11]

A great example is the announcement of two mobile medical apps designed by Apple to work on the Apple Watch. One app creates an electrocardiogram, similar to traditional electrocardiograms, to detect the presence of atrial fibrillation and regular heart rhythm, while the other app analyzes pulse rate data to identify irregular heart rhythms suggestive of atrial fibrillation and notify the user. The FDA worked closely with the company as they developed and tested these software products, which may help millions of users identify health concerns more quickly. Health care products on ubiquitous devices, like smart watches, may help users seek treatment earlier and will truly empower them with more information about their health.

American Heart Association News also commented on the Apple Watch: [12]

This can be an addition to our growing armamentarium to diagnose AFib, which can be intermittent and asymptomatic,” said Dr. Lin Yee Chen, co-director of the Atrial Fibrillation Center at University of Minnesota Health Heart Care. He had not seen the device or learned any details beyond the basics provided by Apple.

“This is an exciting technology which hopefully can help to alleviate the public health burden of AFib by diagnosing it earlier and taking steps to prevent complications,” he said.

AFib affects up to 6.1 million people in the United States, a number that researchers expect will double by 2050. Untreated, AFib doubles the risk of heart-related death and increases a person’s chance of having a stroke fivefold. Apple considered this development so important that it invited Dr. Ivor Benjamin – president of the American Heart Association – to be on stage for the announcement at company headquarters in Cupertino, California.

“Capturing meaningful data about a person’s heart, in real time, is changing the way we practice medicine,” said Benjamin, who is also director of the Cardiovascular Center at the Medical College of Wisconsin. “In my experience, people often report symptoms that are absent during their medical visits. That’s why information is vital – information about a person’s daily lifestyle choices and their specific health data.”

Perez et al studied the ability of the Apple Watch to identify atrial fibrillation during typical use ion 2019.[13] 419,297 patricipants were recruited.

Over a median of 117 days of monitoring 2161 participants (0.52%) received notifications of irregular pulse. Among the 450 participants who returned ECG patches containing data that could be analyzed – which had been applied, on average, 13 days after notification – atrial fibrillation was present in 34%.

The pros and cons of remote EKG monitoring for atrial fibrillation were summarized in 2018 by Aaron Carroll in the New York Times:[14]

With respect to monitoring from a doctor, the Food and Drug Administration “cleared” the app — an easier hurdle to surmount than “approval.” But it specifically said people with diagnosed atrial fibrillation, one of the most common heart arrhythmias, should not be using the app.

If that’s the case, the major potential for the device — which will arrive later this year — is to pick up arrhythmias in otherwise healthy people. That’s still a big selling point. Picking up abnormal function earlier could theoretically lead to improvements in health, such as reductions in strokes.

But just because something seems like a good idea doesn’t mean it is. No screening test is perfect. In the simplest sense, whenever we consider the results of medical tests, they can be “positive” or “negative.”

In general, we would like people who are sick to have a positive screening result, and people who are well to have a negative result. Unfortunately, people who are sick sometimes have a negative result. Those are false negatives. People who are well sometimes have a positive result. Those are false positives.

Both of these outcomes are worrisome. A false negative might leave someone who needs medical help with a mistaken sense of assurance. Given that relatively few people have serious, undiagnosed arrhythmias with no symptoms (if people did, we would be screening for this more often), this isn’t the major concern. False positives are, because they cost us time and money, as well as cause emotional distress.

The health care system is already busy, if not overloaded. No physician wants to field calls from patients who have no problems. Such patients will require visits and further testing, and will potentially receive interventions. They’ll generate bills and harms without benefits.

The watch will also have an “irregular rhythm” notification feature, which alerts people to potential problems. There’s every reason to believe it will generate many false positives. Before granting clearance, the F.D.A. reviewed data collected by the Stanford Heart study for 266 people who got such a notification. Most of the notifications were wrong.

The study wasn’t peer reviewed, so we don’t know for sure, but this was also a population for whom atrial fibrillation might be more common than in those who might use the watches. People who buy the latest Apple watch will most likely be younger, healthier, wealthier and more plugged into the health care system — and less likely to remain undiagnosed.

This is one of the major problems with such a device. The people most in need of it, those who might benefit from tests and distance monitoring, are the least likely to get it. If we truly believed this was a medical test beneficial to the general population, insurance should pay for it. No one is suggesting that should happen.

In fact, many experts don’t think it makes sense to have universal cardiac monitoring of the general public. The United States Preventive Services Task Force has issued a “D” recommendation for screening asymptomatic adults at low risk. The group doesn’t think there’s enough evidence to recommend screening of adults at intermediate or high risk. It doesn’t even think there’s enough evidence to recommend screening adults 65 or older, who are at higher risk, for atrial fibrillation.

The task force bases these recommendations on good research. A large randomized controlled trial of echocardiographic screening for many heart problems did not demonstrate that such screening offered any benefits in reducing death or the risk of heart attacks or stroke in middle-aged people. And these are scans much more robust than will be available with the new Apple Watch.

None of this prevented the American Heart Association from heralding this new function, although it’s not clear where the group’s enthusiasm comes from. Dr. Ivor Benjamin, the association president, appeared at the official announcement of the watch and praised the advancement for tools that “help fight heart heart diseae.” (The A.H.A. does not officially endorse the watch, or any other specific products.)

Dr. Carroll concludes: “I own one [Apple Watch] because I want it, not because I need it. That’s the same criterion you should use, too.”

In conclusion, personal health technology has the capability of detecting atrial fibrillation. However, a false positive screening test will increase patient anxiety, lead to perhaps unnecessary testing, and increase medical cost. These are usually single lead systems and thus may be less accurate than a 12 lead ECG. Also, there are possible privacy concerns when medical data is transmitted over the internet. Screening for atial fibrillation has not yet been endorsed by medical organizations, but many physicians recommend it for high risk patients.

  1. Go AS, Hylek EM, Phillips KA, et al. Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study. JAMA 2001; 285:2370.
  2. Lloyd-Jones DM, Wang TJ, Leip EP, et al. Lifetime risk for development of atrial fibrillation: the Framingham Heart Study. Circulation 2004; 110:1042.
  3. Screening for Atrial Fibrillation With Electrocardiography US Preventive Services Task Force Recommendation Statement. US Preventive Services Task Force. JAMA. 2018;320(5):478-484.
  4. GiuseppeBorianiabRenate BSchnabelbcdJeff SHealeybeRenato DLopesbfNicoleVerbiest-van GurpgTrudieLobbanbhJohn ACammbiBenFreedmanbjk, Consumer-led screening for atrial fibrillation using consumer-facing wearables, devices and apps: A survey of health care professionals by AF-SCREEN international collaboration. European Journal of Internal Medicine. Volume 82, December 2020, Pages 97-104.
  5. Effect of a Home-Based Wearable Continuous ECG Monitoring Patch on Detection of Undiagnosed Atrial Fibrillation: The mSToPS Randomized Clinical Trial. Steinhubl SR, Waalen J, Edwards AM, Ariniello LM, Mehta RR, Ebner GS, Carter C, Baca-Motes K, Felicione E, Sarich T, Topol EJ. JAMA. 2018;320(2):146.
  8. Assessment of Remote Heart Rhythm Sampling Using the AliveCor Heart Monitor to Screen for Atrial Fibrillation The REHEARSE-AF Study. Halcox J, Wareham K, Cardew A, et al. Circulation. 2017;136:1784–1794.
  9. Assessing the accuracy of an automated atrial fibrillation detection algorithm using smartphone technology: The iREAD Study William A, Kanbour, M, Callahan T, et al. HeartRhythm2018;15:1561–1565.
  12. Perez MV, Mahaffey KW, Hedlin H, Rumsfeld JS, Garcia A, Ferris T, Balasubramanian V, Russo AM, Rajmane A, Cheung L, Hung G, Lee J, Kowey P, Talati N, Nag D, Gummidipundi SE, Beatty A, Hills MT, Desai S, Granger CB, Desai M, Turakhia MP, Apple Heart Study Investigators. Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation. N Engl J Med. 2019;381(20):1909.

Disclaimer: Since healthcare is complicated and personal, you should discuss these topics with your healthcare provider before applying this information to your own health. This website does not intend to diagnose or treat any disease or medical condition. Its only purpose is to assist people to monitor their health at home under the supervision of their healthcare provider.

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