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Updated: Sep 30, 2025
Patient Directed Recording of a Bipolar Three-Lead Electrocardiogram using a Smartwatch with ECG Function
Published on: December 11, 2019
A comparison of manual electrocardiographic interval and waveform analysis in lead 1 of 12-lead ECG and Apple Watch
Nabeel Saghir1, Arjun Aggarwal1, Nisha Soneji1
1Dell Medical School at The University of Texas at Austin, Austin, Texas - Department of Internal Medicine.
Background:
The Apple Watch Series 4 (AW) can detect atrial fibrillation and perform a single-lead electrocardiogram (ECG), but the clinical accuracy of AW ECG waveforms compared to lead 1 of a 12-lead ECG is unclear.
Objective:
The purpose of this study was to assess the accuracy of interval measurements on AW ECG tracings in comparison to lead 1 on a 12-lead ECG.
Methods:
We obtained ECGs at a university hospital of healthy volunteers age >18 years. ECG waveforms were measured with calipers to the nearest 0.25 mm. When possible, 3 consecutive waveforms in lead 1 were measured. Waveform properties, including intervals, were recorded. Concordance correlation coefficients and Bland-Altman plots were used to assess level of agreement between devices.
Results:
Twelve-lead (n = 113) and AW (n = 129) ECG waveforms from 43 volunteers (mean age 31 years; 65% female) were analyzed. Sinus rhythm interpretation between devices was 100% concordant. No arrhythmias were recorded. Mean difference (d) for heart rate was 1.16 ± 4.33 bpm (r = 0.94); 3.83 ± 113.54 ms for RR interval (r = 0.79); 5.43 ± 17 ms for PR interval (r = 0.83); -6.89 ± 14.81 ms for QRS interval (r = 0.65); -11.27 ± 22.9 ms for QT interval (r = 0.79); and -11.67 ± 27 ms for QTc interval (r = 0.57). There was moderate (d <40 ms) to strong (d <20 ms or < 5 bpm) agreement between devices represented by Bland-Altman plots.
Conclusion:
The AW produces accurate ECGs in healthy adults with moderate to strong agreement of basic ECG intervals.
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