# Smartwatch irregular-pulse detection Technology · id `cardio:wearable-rhythm-detection` · Cardiovascular Atlas · release `f6f6f1b6f50379ed` (public) > General information from published sources, not medical advice, and not reviewed by clinicians. Check the cited source before relying on anything here. The atlas's own text and curation may be reused under Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0, https://creativecommons.org/licenses/by-nc/4.0/): credit the atlas, and do not use it commercially. See the atlas About page. Text quoted from a source stays under that source's own terms, given as the source's reuse\_basis. The atlas's reuse terms do not cover it. The downloads list each quotation with its source in third\_party\_quotations. Also called: Wearable rhythm detection; Smartwatch rhythm detection Browse, organ or system: Heart Browse, condition area: Heart rhythm problems ## In plain language Watches and similar worn devices can check the pulse with light sensors and flag a pulse pattern that may be atrial fibrillation. A flag is a prompt to get checked, not a diagnosis. In the Apple Heart Study, only 2161 of 419,297 participants received an alert, and 34% of those who returned an analyzable ECG patch had atrial fibrillation on it. ## Technical summary Photoplethysmography on wearable devices. The Apple Heart Study abstract says optical sensors on wearable devices can detect irregular pulses. In that study a smartwatch algorithm flagged a possible irregular pulse, which started a telemedicine visit and a mailed ECG patch. FDA's device-type name for De Novo product code QDB is photoplethysmograph analysis software for over-the-counter use. The study measured agreement between alerts and an ECG patch. It did not measure stroke or other clinical outcomes. Other detection devices, such as handheld or phone-case ECG sensors, are not covered here. ## Claims, with the population each applies to ## Context: US adults with a compatible iPhone and Apple Watch and no self-reported atrial fibrillation (Apple Heart Study) Recipient: Adult; Population: People aged 22 or older who lived in the United States, owned a compatible iPhone and Apple Watch, had no self-reported diagnosis of atrial fibrillation or atrial flutter, and were not on anticoagulation therapy (registry exclusion criteria).; Care setting: Remote and siteless. People consented and took part through a smartphone app with no on-site visits. After a notification, the study started a telemedicine visit and mailed an ECG patch to the participant.; Geography: United States (the registry lists only the United States as a country); Life stage: Adults aged 22 or older (registry minimum age). The abstract reports one result separately for participants aged 65 or older.; Follow-up: Median of 117 days of monitoring. An ECG patch was worn for up to 7 days (the registry gives up to 8 days of ambulatory monitoring) and was applied on average 13 days after a notification. Surveys were sent 90 days after a notification and at the end of the study. ### In the Apple Heart Study, 419,297 participants with no self-reported atrial fibrillation used an Apple Watch and iPhone app, and were followed for a median of 117 days. 2161 of them (0.52%) received a notification of an irregular pulse. Of the 450 notified participants who returned ECG patches with data that could be analyzed (applied on average 13 days after the notification), 34% had atrial fibrillation on the patch (97.5% confidence interval 29 to 39), and 35% of those aged 65 or older (97.5% CI 27 to 43). Separately, the positive predictive value among notified participants was 0.84 (95% CI 0.76 to 0.92) for atrial fibrillation on the ECG at the same time as a later irregular pulse notification, and 0.71 (97.5% CI 0.69 to 0.74) for atrial fibrillation on the ECG at the same time as an irregular tachogram. Of 1376 notified participants who returned a 90-day survey, 57% contacted health care providers outside the study. The paper reports no serious app-related adverse events. - Category: Description - Evidence stage: Human feasibility - Certainty: Certainty not assessed - Applies to: Recipient: Adult; Population: People aged 22 or older who lived in the United States, owned a compatible iPhone and Apple Watch, had no self-reported diagnosis of atrial fibrillation or atrial flutter, and were not on anticoagulation therapy (registry exclusion criteria).; Care setting: Remote and siteless. People consented and took part through a smartphone app with no on-site visits. After a notification, the study started a telemedicine visit and mailed an ECG patch to the participant.; Geography: United States (the registry lists only the United States as a country); Life stage: Adults aged 22 or older (registry minimum age). The abstract reports one result separately for participants aged 65 or older.; Follow-up: Median of 117 days of monitoring. An ECG patch was worn for up to 7 days (the registry gives up to 8 days of ambulatory monitoring) and was applied on average 13 days after a notification. Surveys were sent 90 days after a notification and at the end of the study. - Limitations: Single-group study with no comparison group, using the study's own research app. The result is not about the FDA-authorized feature itself, and the sources read do not say how the two relate. The registry lists as outcomes the share of notified participants with AF on the ECG, agreement between the app and the ECG, and contact with a health care provider. It lists no stroke or other clinical outcome, so the study does not show that notifications prevent strokes. Only 450 of the 2161 notified participants returned analyzable patches. The abstract gives the 34% (97.5% CI) and the 0.84 (95% CI) as separate measures, and they are not the same quantity. The registry enrollment (419927) and the abstract recruitment count (419,297) differ and are not reconciled. Participants were self-selected owners of a compatible phone and watch, and the abstract does not describe their health or demographics. Abstract only; the PMC copy is not in the Open Access subset and the full text was not read. - Last checked: 2026-10-14 - Sources: 1. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 1. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Recruitment count. 2. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 2. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Median monitoring and notification count. 3. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 3, fragment 1. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Patch count and timing (first fragment). 4. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 3, fragment 2. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Share with AF on the patch (second fragment). 5. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 3, fragment 3. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Share aged 65 or older (third fragment). 6. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 4, fragment 1. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Positive predictive value for the notification (first fragment). 7. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 4, fragment 2. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Positive predictive values for the notification and the tachogram (second fragment). 8. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 4, fragment 3. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Tachogram measure (third fragment). 9. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 5. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Contact with providers after a notification. 10. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, RESULTS, sentence 6. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: No serious app-related adverse events reported. 11. Supports: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, CONCLUSIONS, sentence 1. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: The authors' own summary: the chance of a notification was low. 12. Background: Large-Scale Assessment of a Smartwatch to Identify Atrial Fibrillation (Publication, edition PubMed record (abstract and bibliographic data) fetched 2026-10-14 through NCBI E-utilities. The PMC copy PMC8112605 is not in the PMC Open Access subset, so its full text was not fetched. The version of record was not fetched. Full-text facts are not used.) Locator: Abstract, METHODS, sentence 4, fragment 1. Retrieved 2026-10-14T18:18:40Z. Source state: Current. Snapshot hash: 3a30de5458d89e92e2f2f19442f726ff4149eb0abd8ff3ce4e0cd88072ec4315. How it applies: Main objectives of the study (first fragment). 13. Background: Apple Heart Study: Assessment of Wristwatch-Based Photoplethysmography to Identify Cardiac Arrhythmias (Registry, edition ClinicalTrials.gov API v2 record fetched 2026-10-14. Last update posted 2020-03-30.) Locator: protocolSection.outcomesModule.primaryOutcomes\[0\].measure. Retrieved 2026-10-14T18:18:38Z. Source state: Current. Snapshot hash: d32097cfe2767d4a1fb8337dbd9bf84990d1608aae0e10402628075e51c296ba. How it applies: Registry primary outcome 1. 14. Background: Apple Heart Study: Assessment of Wristwatch-Based Photoplethysmography to Identify Cardiac Arrhythmias (Registry, edition ClinicalTrials.gov API v2 record fetched 2026-10-14. Last update posted 2020-03-30.) Locator: protocolSection.outcomesModule.primaryOutcomes\[1\].measure. Retrieved 2026-10-14T18:18:38Z. Source state: Current. Snapshot hash: d32097cfe2767d4a1fb8337dbd9bf84990d1608aae0e10402628075e51c296ba. How it applies: Registry primary outcome 2. 15. Background: Apple Heart Study: Assessment of Wristwatch-Based Photoplethysmography to Identify Cardiac Arrhythmias (Registry, edition ClinicalTrials.gov API v2 record fetched 2026-10-14. Last update posted 2020-03-30.) Locator: protocolSection.outcomesModule.secondaryOutcomes\[0\].measure. Retrieved 2026-10-14T18:18:38Z. Source state: Current. Snapshot hash: d32097cfe2767d4a1fb8337dbd9bf84990d1608aae0e10402628075e51c296ba. How it applies: Registry secondary outcome 1. 16. Background: Apple Heart Study: Assessment of Wristwatch-Based Photoplethysmography to Identify Cardiac Arrhythmias (Registry, edition ClinicalTrials.gov API v2 record fetched 2026-10-14. Last update posted 2020-03-30.) Locator: protocolSection.outcomesModule.secondaryOutcomes\[1\].measure. Retrieved 2026-10-14T18:18:38Z. Source state: Current. Snapshot hash: d32097cfe2767d4a1fb8337dbd9bf84990d1608aae0e10402628075e51c296ba. How it applies: Registry secondary outcome 2. 17. Background: Apple Heart Study: Assessment of Wristwatch-Based Photoplethysmography to Identify Cardiac Arrhythmias (Registry, edition ClinicalTrials.gov API v2 record fetched 2026-10-14. Last update posted 2020-03-30.) Locator: protocolSection.designModule.enrollmentInfo.count. Retrieved 2026-10-14T18:18:38Z. Source state: Current. Snapshot hash: d32097cfe2767d4a1fb8337dbd9bf84990d1608aae0e10402628075e51c296ba. How it applies: Registry enrollment count, which differs from the abstract. ## Connected pages - Alerts compared with an ECG patch in the Apple Heart Study: Atrial fibrillation (AF) (`cardio:atrial-fibrillation`) [a claim, not a settled fact; see claim `cardio:claim-apple-heart-study-alerts` and its context] - Detection outside the clinic: AF that causes no symptoms is hard to diagnose (`cardio:bottleneck-undiagnosed-af`) - Filed under this front: Devices and monitoring (`cardio:front-devices-and-monitoring`) - Used by: Irregular Rhythm Notification Feature (Apple) (`cardio:apple-irregular-rhythm-notification`) - Investigated in: Apple Heart Study (`cardio:apple-heart-study`) ## Provenance Content hash: bf90005254096a38b0e7504e4928cf95301cdf20d40ac2c3e98b0ba8a862fed5 Last substantive edit: 2026-10-14 Evidence last checked: 2026-10-14