Smart Device Detection of Atrial Fibrillation: BASEL Wearable Study

Quick Takes

  • Inconclusive tracings were produced by smart devices approximately one-fourth of the time, requiring interpretation by a physician, suggesting further improvements in these algorithms are warranted.
  • For interpretable tracings, the sensitivity and specificity were similar between the devices.
  • Long-term adherence and monitoring through these devices needs to be verified in a clinical setting with a cohort of patients possibly at risk.

Study Questions:

Does the sensitivity and specificity for detection of atrial fibrillation (AF) differ between available smart devices?


The BASEL Wearable Study is a prospective, single-center study that enrolled eligible patients between April 2012 and May 2022. Patients were eligible if they presented with the need for management of AF, including catheter ablation procedures, cardioversions, pacemakers, or defibrillator implantation. Those with missing electrocardiographic (ECG) data were excluded. Five wearable smart devices—all of which are commercially available and CE and FEA marked—(Apple Watch 6, AliveCor KardiaMobile or KardiaMobile 6L, Fitbit Sense, Samsung Galaxy Watch 3, and Withings Scan Watch) were included. If feasible, all smartwatches were worn on the left wrist. All SL-ECG recordings from the smart devices and 12-lead ECGs were reviewed by two cardiologists blinded to the device recording the tracing. Tracings were coded as sinus rhythm, AF, or inconclusive. ECGs of inconsistent diagnosis (disagreement between the two initial cardiologists’ diagnoses) were reviewed and assessed by a third cardiologist.


A total of 201 patients were included, of which 31% were women, and the median age was 67 years. AF was present in 62 patients (31%). Sensitivity and specificity for the detection of AF were comparable between devices: 85% and 75% for the Apple Watch 6, 85% and 75% for the Samsung Galaxy Watch 3, 58% and 75% for the Withings Scanwatch, 66% and 79% for the Fitbit Sense, and 79% and 69% for the AliveCor, respectively. The rate of inconclusive tracings (the algorithm was unable to determine the heart rhythm) was 18%, 17%, 24%, 21%, and 26% for the Apple Watch 6, Samsung Galaxy Watch 3, Withings Scan Watch, Fitbit Sense, and AliveCor (p < 0.01 for pairwise comparison), respectively. By manual review of inconclusive tracings, the rhythm could be determined in 955 of 969 (99%) single-lead ECGs. Patients were surveyed for useability; the Apple Watch was ranked first (39% of participants).


The authors conclude that differences in the number of inconclusive tracings diminish the sensitivity and specificity of the smart devices. In a clinical setting, manual review of tracings is required in approximately one-fourth of cases.


As the authors note, smart devices are limited by the number of inconclusive tracings, which require review by a cardiologist. This suggests that caution be used when making clinical assessments using smart devices. It should also be noted that wearers had concerns regarding long-term use.

Clinical Topics: Arrhythmias and Clinical EP, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Catheter Ablation, Defibrillators, Electric Countershock, Electrocardiography, Pacemaker, Artificial, Secondary Prevention, Smartphone, Wearable Electronic Devices

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