Anker, Stefan D.

Butler, Javed

Haverkamp, Wilhelm

English

Institutional Repository of the Freie Universität Berlin

European Journal of Heart Failure (2021) 23, 850–853 VIEWPOINTdoi:10.1002/ejhf.2194Can we trust a smartwatch ECG?Potential and limitationsWilhelm Haverkamp1*, Javed Butler2, and Stefan D. Anker11Department of Cardiology (CVK); and Berlin Institute of Health Center for Regenerative Therapies (BCRT); German Centre for Cardiovascular Research (DZHK) partner siteBerlin, Charité Universitätsmedizin Berlin, Berlin, Germany; and 2Department of Medicine, University of Mississippi, Jackson, MS, USAThe ability to record a 30 s single-lead electrocardiogram (ECG)at any time and as often as desired is a relatively new functionalityof smartwatches that has been purported as a potentially usefulmedical technology advancement. Advertisers see this as the lat-est life-saving feature added to advanced smartwatches.1 From aphysician’s perspective, this new technology is especially of inter-est since this may facilitate atrial fibrillation detection automaticallyin otherwise asymptomatic individuals, but this remains currentlyunconfirmed. Greater than 10% of individuals with the arrhyth-mias remain undiagnosed during their lifetime because they do nothave any symptoms and among patients with acute cerebral stroke,about 20% have a new atrial fibrillation diagnosis.2 The early detec-tion of atrial fibrillation would allow early initiation of anticoagula-tion therapy, which may lead to a reduction in the number of cere-bral strokes and other arrhythmia-related morbidity and mortality.3Designed and introduced as tools for health monitoring, it wasinitially unclear whether ECG-enabled smartwatches are for diag-nostic purposes. The manufacturers underscore explicitly that thisis indeed not the case. According to the user manuals accom-panying the devices, ECG is recorded for information purposesonly and is not intended to replace traditional methods of elec-trocardiographic assessment for medical diagnosis. However, themanufacturers consider their apps which provide the ECG functionto be medical products. All ECG apps (except those by Withings)have both CE certification in Europe, and Food and Drug Admin-istration clearance as per the 510(k) pathway in the USA.4–7 Thefulfilment of regulatory requirements is a precondition for mar-keting. These inconsistencies have caused confusion, particularlyamong physicians. The recently updated version of the EuropeanSociety of Cardiology (ESC) guidelines for the management of atrialfibrillation3 explicitly state that a smartwatch-based ECG can beused to diagnose atrial fibrillation and that no confirmation byanother ECG procedure is needed (provided that the arrhythmialasts for 30 s, which is exactly the time needed for a smartwatchrecording). The same guidelines also state that the devices may beused for screening for atrial fibrillation. The feasibility of such ascreening has been demonstrated by two large studies published in*Corresponding author. Division of Cardiology and Metabolism, Department of Cardiology, Charité – University Hospital; Augustenburger Platz 1, 13353 Berlin, Germany. Tel:+49 30 3985270, Email: wilhelm.haverkamp@charite.de............................................................................................................... 2019, the Apple Heart Study8 with more than 400 000 participants,and the Huawei Heart Study9 with more than 180 000 participants.However, even though both studies included larger numbers ofpatients, we contend that they do not necessarily provide defini-tive proof for the diagnostic accuracy of smartwatch ECGs underreal-word conditions as they did not have a positive control. Indeed,the ESC atrial fibrillation guidelines highlight the need for furtherclinical studies aiming to validate the new technique.3Since it will take years before the results of such studies will beavailable, in this viewpoint we sought to provide a closer look atthe algorithms underlying the ECG function of the ECG-enabledsmartwatches currently available in Europe (Table 1). These algo-rithms reflect and correlate with the diagnostic capabilities of thedevices.Diagnostic accuracy of theimplemented algorithmsAll ECG-enabled smartwatches are equipped with software appli-cations that allow atrial fibrillation to be diagnosed automatically.Some of the smartwatches (Apple and Withings) allow atrial fibril-lation screening using photoplethysmographic pulse wave analysis.If atrial fibrillation is suspected, the user is notified and asked torecord an ECG. For the diagnosis of atrial fibrillation, sensitivitiesand specificities exceeding 95% have been reported.4–7 However,it should be noted that these studies were performed under stan-dardized research conditions and provide data on evaluable ECGsonly; approximately 10–20% of ECGs recorded with a smartwatchare not evaluable (e.g. due to artefacts resulting from body motionor poor electrode contact).The data compiled in Table 1 suggest that diagnostic accuracyis likely to be significantly lower in everyday use and in clinicallyrelevant higher rate scenarios. Atrial fibrillation with a ventricularrate below 50 bpm is not detected by any of the smartwatches. Athigh heart rates, there is a threshold above which atrial fibrillationis no longer tested for. This is 120 bpm for most watches. A revised© 2021 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use anddistribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. 18790844, 2021, 6, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2194 by Charité - Universitaetsmedizin, Wiley Online Library on [09/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons LicenseViewpoint 851Table 1 Electrocardiogram-enabled smartwatches available in Europe (only devices with CE marking are considered)Smartwatch Rhythms detected by the ECG functiona Comment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .AppleApple Watch Series 4, 5and 6Version 2.0:- Sinus rhythm: 50–100 bpm- AF: 50–150 bpm- InconclusiveVersion 1.0:- Sinus rhythm: 50–100 bpm- AF: 50–120 bpm- InconclusiveECG app and AF screening app cleared byFDA (08/2018) and CE certified(03/2019). Updated ECG app (version2.0) available in Europe since 01/2021.FitbitSense- Sinus rhythm: 50–120 bpm- AF: 50–120 bpm- InconclusiveECG app CE certified (08/2020) and FDAcleared (08/2020). AF screening not yetavailable.SamsungGalaxy Watch Active 2,Galaxy Watch 3- Sinus rhythm: 50–100 bpm- AF: 50–120 bpm- InconclusiveECG app FDA cleared (08/2020) and CEcertified (12/2020). Announced to beavailable in Europe in spring 2021.WithingsMove ECG, Scanwatch- Sinus rhythm- AFb- InconclusiveECG app CE certified (MOVE ECG:06/2019, Scanwatch 06/2020). FDAclearance is pending.AF, atrial fibrillation; CE, Conformité Européenne; ECG, electrocardiogram; FDA, Food and Drug Administration.aFor further details please refer to the cited references.bThe available information is inconclusive, according to the manufacturer no limits for AF detection, no validation data.version of the Apple algorithm now detects atrial fibrillation atventricular rates up to 150 bpm.10 However, the accuracy of thealgorithm is significantly lower at ventricular rates above 100 bpmthan at ventricular rates of 50–99 bpm (98.3% vs. 83%).7 In thiscontext, it is important to note that new-onset atrial fibrillationclinically has ventricular rates above 120 bpm in about one-third ofcases, and it is not uncommon for the rate to exceed 150 bpm.8Figure 1 gives examples showing that atrial fibrillation may remainundiagnosed by a smartwatch when heart rate exceeds a certainlimit.Some devices use photophlethysmography to detect pulse irreg-ularities (Table 1). Photophlethysmography is a simple optical tech-nique, which is based on the detection of changes in blood volumein the peripheral circulation.11 It is highly accurate at measuringheart rate in sinus rhythm at rest (correlation coefficient of 0.96).12However, it is sensitive to artefacts (e.g. body movement and poorsensor contact). Diagnosing atrial fibrillation can be quite challeng-ing, particularly at higher heart rates.13 Other types of arrhythmiasreduce the diagnostic accuracy.10 False positive result may occur.One episode of pulse irregularity detected by photoplethysmog-raphy is not enough to inform the patient that atrial fibrillationmight be present. In the case of the Apple watch, five out of sixconsecutive photoplethysmographic measurements (performed atrest) need to fulfil the criteria for possible atrial fibrillation beforethe patient receives a message.10 Thus, smartwatch-based screen-ing for atrial fibrillation is a relatively complex procedure. It isparticularly important that measurements are not performed con-tinuously, as one may expect, but only intermittently, the protocolsfor which depend on the manufacturer. This is because such mea-surements consume significant power and the battery life of mostECG-enabled smartwatches is relatively short. .............................................................................................. Clinical implicationsThe algorithms currently used by ECG-enabled smartwatchesshow particularities, which are manufacturer-dependent and signif-icantly limit their diagnostic accuracy. They may lead to both falsepositive and negative diagnoses, resulting in anxiety and unneces-sary further diagnostic testing. Physicians using this new technologytoday should be aware of these limitations. These should be dis-cussed with patients presenting with an ECG-enabled smartwatch.Physician overreading remains mandatory, even when the patientpresents repeatedly with numerous ECG recordings. It has beenknown for decades that computerized interpretation of atrial fib-rillation is a challenge and that incorrect computerized interpre-tation, combined with the failure to correct the erroneous inter-pretation, can result in the initiation of unnecessary and potentiallyharmful medical treatment as well as inappropriate use of medicalresources.14 The outlined limitations should also be appreciatedwhen the devices are used in the context of clinical studies. It islikely that there will be an improvement in diagnostic accuracyin the future, probably in parallel with an increased use of algo-rithms based on artificial intelligence. It is also difficult in somecases to obtain information regarding the way the algorithms ofthe ECG function work. When it comes to trusting new tech-nologies, it is important to have a detailed knowledge about theiralgorithms and processes. This holds also true for ECG-enabledsmartwatches.Conflict of interest: W.H. declares that he has received feesfrom Abbott, Amicus, AstraZeneca, Bayer, Bristol Myers Squibb,Daiichi-Sankyo, Medtronic, Pfizer, and Sanofi. J.B. declares that heserves as a consultant for Abbott, Adrenomed, Amgen, Array,AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb,© 2021 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology. 18790844, 2021, 6, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2194 by Charité - Universitaetsmedizin, Wiley Online Library on [09/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License852 ViewpointFigure 1 Example of two electrocardiograms (ECGs) in the same 56-year-old patient at ventricular rate of 120 bpm (A) and 161 bpm (B).Apple Watch Series 5. (A) The automatic algorithm diagnoses ‘atrial fibrillation’ at a ventricular rate of 120 bpm. The patient is informed thatthe ECG shows signs of atrial fibrillation. (B) Atrial fibrillation persists. The diagnosis is no longer atrial fibrillation, but ‘heart rate over 150bpm’. The patient is informed that the ECG is not checked for signs of atrial fibrillation, because heart rate exceeds 150 bpm.CVRx, G3 Pharmaceutical, Impulse Dynamics, Innolife, Janssen,LivaNova, Luitpold, Medtronic, Merck, Novartis, NovoNordisk,Relypsa, Roche, V-Wave Limited, and Vifor. S.D.A. declares thathe has received fees from Abbott, Actimed, Bayer, BoehringerIngelheim, Brahms, Cardiac Dimension, Impulse Dynamics, Novar-tis, Occlutech, Servier, and Vifor Pharma, and grant support fromAbbott and Vifor Pharma.AcknowledgementOpen access funding enabled and organized by Projekt DEAL. ................................. References1. Caddy B. Can a smartwatch save your life? 26 January 2018. https://www.techradar.com/news/can-smartwatches-save-your-life (23 April 2021).2. Jaakkola J, Mustonen P, Kiviniemi T, Hartikainen JE, Palomäki A, Hartikainen P,Nuotio I, Ylitalo A, Airaksinen KE. Stroke as the first manifestation of atrialfibrillation. PLoS One 2016;11:e0168010.3. Hindricks G, Potpara T, Dagres N, Arbelo E, Bax JJ, Blomström-Lundqvist C,Boriani G, Castella M, Dan GA, Dilaveris PE, Fauchier L, Filippatos G, KalmanJM, La Meir M, Lane DA, Lebeau JP, Lettino M, Lip GYH, Pinto FJ, ThomasGN, Valgimigli M, Van Gelder IC, Van Putte BP, Watkins CL; ESC ScientificDocument Group. 2020 ESC Guidelines for the diagnosis and management ofatrial fibrillation developed in collaboration with the European Association ofCardio-Thoracic Surgery (EACTS). Eur Heart J 2021;42:373–498.© 2021 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology. 18790844, 2021, 6, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2194 by Charité - Universitaetsmedizin, Wiley Online Library on [09/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons LicenseViewpoint 8534. U.S. Food and Drug Administration. Electrocardiograph software forover-the-counter use. Apple ECG app. August 14, 2018. https://www.accessdata.fda.gov/cdrh_docs/reviews/DEN180044.pdf (23 April 2021).5. U.S. Food and Drug Administration. Electrocardiograph software forover-the-counter use. Fitbit ECG App. September 11, 2020. http://www.accessdata.fda.gov/cdrh_docs/pdf20/K200948.pdf (23 April 2021).6. U.S. Food and Drug Administration. Electrocardiograph software for over-the-counter use. Samsung ECG Monitor Application. August 4, 2020. http://www.accessdata.fda.gov/cdrh_docs/pdf20/K201168.pdf (23 April 2021).7. Withings. Scan Watch. https://support.withings.com/hc/de/articles/360012786977-ScanWatch-Benutzerhandbuch (23 April 2021).8. Perez MV, Mahaffey KW, Hedlin H, Rumsfeld JS, Garcia A, Ferris T, Balasubrama-nian 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, TurakhiaMP; Apple Heart Study Investigators. Large-scale assessment of a smartwatch toidentify atrial fibrillation. N Engl J Med 2019;381:1909–1917.9. Guo Y, Wang H, Zhang H, Liu T, Liang Z, Xia Y, Yan L, Xing Y, Shi H,Li S, Liu Y, Liu F, Feng M, Chen Y, Lip G; MAFA II Investigators. Mobile ........................................ photoplethysmographic technology to detect atrial fibrillation. J Am Coll Cardiol2019;74:2365–2375.10. Apple. Using Apple Watch for Arrhythmia Detection. December 2020. https://www.apple.com/healthcare/docs/site/Apple_Watch_Arrhythmia_Detection.pdf(23 April 2021).11. Pereira T, Tran N, Gadhoumi K, Pelter MM, Do DH, Lee RJ, Colorado R, Meisel K,Hu X. Photoplethysmography based atrial fibrillation detection: a review. NPJ DigitMed 2020;3:3.12. Koshy AN, Sajeev JK, Nerlekar N, Brown AJ, Rajakariar K, Zureik M,Wong MC, Roberts L, Street M, Cooke J, Teh AW. Smart watchesfor heart rate assessment in atrial arrhythmias. Int J Cardiol 2018;266:124–127.13. Harju J, Tarniceriu A, Parak J, Vehkaoja A, Yli-Hankala A, Korhonen I. Monitoringof heart rate and inter-beat intervals with wrist plethysmography in patients withatrial fibrillation. Physiol Meas 2018;39:065007.14. Bogun F, Anh D, Kalahasty G, Wissner E, Bou Serhal C, Bazzi R, DouglasWeaver W, Schuger C. Misdiagnosis of atrial fibrillation and its clinical conse-quences. Am J Med 2004;117:636–642.© 2021 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology. 18790844, 2021, 6, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2194 by Charité - Universitaetsmedizin, Wiley Online Library on [09/12/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Can we trust a smartwatch ECG? Potential and limitations

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Can we trust a smartwatch ECG? Potential and limitations

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