Accuracy of wrist-worn heart rate monitors for rate control assessment in atrial fibrillation

Int J Cardiol. 2020 Feb 1;300:161-164. doi: 10.1016/j.ijcard.2019.11.120. Epub 2019 Nov 18.


Background: Wrist-worn heart rate (HR) monitors are increasingly popular. A paucity of data exists on their accuracy in atrial fibrillation (AF) in ambulatory patients. We sought to assess the HR accuracy of two commercially available smart watches [SW] (Fitbit Charge HR [FB] and Apple Watch Series 3 [AW]) compared with Holter monitoring in an ambulant patient cohort.

Methods: Thirty-two participants ≥18 years referred for 24-hour Holter monitoring were prospectively recruited. Each participant was randomly allocated to wear either a FB or AW along with their Holter monitor.

Results: Across all devices, 53,288 heart rate values were analysed from 32 participants. Twenty wore the AW (17 had persistent AF and 3 had sinus rhythm [SR]) while 12 participants wore the FB (9 in persistent AF and 3 in SR). Participants in SR demonstrated strong agreement compared to Holter monitoring (bias <1 beat, limits of agreement [LoA] -11 to 11 beats). In AF, both devices underestimated HR measurements (bias -9 beats, LoA -41 to 23). The degree of underestimation was more pronounced when HR > 100 bpm (bias of -28 beats for HR range 100-120 bpm, -48 for 120-140 bpm, and -69 for >140 bpm) compared to a slower HR (bias of -6 for HR range 80-100 bpm, <1 for 60-80 bpm, and -1 for <60 bpm).

Conclusion: In ambulatory patients, smartwatches underestimated HR in AF particularly at HR ranges >100 bpm. Further improvements in device technology are needed before integrating them into the clinical management of rate control in AF.

Keywords: Accuracy; Arrhythmia; Atrial fibrillation; Heart rate; Smart watch.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Atrial Fibrillation / diagnosis*
  • Atrial Fibrillation / physiopathology*
  • Electrocardiography, Ambulatory / instrumentation
  • Electrocardiography, Ambulatory / standards*
  • Female
  • Heart Rate / physiology*
  • Humans
  • Male
  • Middle Aged
  • Wearable Electronic Devices / standards*