Key result
Smartwatch QTc measurements approximate 12-lead ECGs but only calculate values in ~56% of patients.
Why the study?
Automated QTc measurements from a single lead ECG smartwatch require clinical validation against manual QTc measurements from 12-lead ECGs to assess accuracy and reliability.
Does automated QTc measurement using a single-lead smartwatch ECG agree with manual 12-lead ECG measurement in patients referred for cardiac workup?
Observational (n=317)
Blinded assessors
No
Does automated QTc measurement using a single-lead smartwatch ECG agree with manual 12-lead ECG measurement in patients referred for cardiac workup?
Mean Difference: 6.6 (95% CI -59–72)
While a direct-to-consumer smartwatch showed fair to good agreement with manual 12-lead ECG for QTc measurement, its automated algorithm could only calculate QTc in about half of patients, limiting its current clinical utility.
May not support routine smartwatch QTc use in cardiac evaluation; leaves open need for algorithm refinement and prospective validation.
Introduction: The Withings Scanwatch (Withings SA, Issy les Moulineaux, France) offers automated analysis of the QTc. We aimed to compare automated QTc-measurements using a single lead ECG of a novel smartwatch (Withings Scanwatch, SW-ECG) with manual-measured QTc from a nearly simultaneously recorded 12-lead ECG. Methods: We enrolled consecutive patients referred to a tertiary hospital for cardiac workup in a prospective, observational study. The QT-interval of the 12-lead ECG was manually interpreted by two blinded, independent cardiologists through the tangent-method. Bazett's formula was used to calculate QTc. Results were compared using the Bland-Altman method. Results: A total of 317 patients (48% female, mean age 63 ± 17 years) were enrolled. HR-, QRS-, and QT-intervals were automatically calculated by the SW in 295 (93%), 249 (79%), and 177 patients (56%), respectively. Diagnostic accuracy of SW-ECG for detection of QTc-intervals ≥ 460 ms (women) and ≥ 440 ms (men) as quantified by the area under the curve was 0.91 and 0.89. The Bland-Altman analysis resulted in a bias of 6.6 ms [95% limit of agreement (LoA) -59 to 72 ms] comparing automated QTc-measurements (SW-ECG) with manual QTc-measurement (12-lead ECG). In 12 patients (6.9%) the difference between the two measurements was greater than the LoA. Conclusion: In this clinical validation of a direct-to-consumer smartwatch we found fair to good agreement between automated-SW-ECG QTc-measurements and manual 12-lead-QTc measurements. The SW-ECG was able to automatically calculate QTc-intervals in one half of all assessed patients. Our work shows, that the automated algorithm of the SW-ECG needs improvement to be useful in a clinical setting.
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Mannhart et al. (2022) conducted an observational in Cardiac workup (n=317). Automated QTc measurement using Withings Scanwatch vs. Manual QTc measurement from a 12-lead ECG was evaluated on Agreement between automated and manual QTc measurements (bias of 6.6 ms, 95% CI -59 to 72). Automated smartwatch QTc measurements showed a bias of 6.6 ms (limits of agreement -59 to 72 ms) compared to manual 12-lead ECGs, but the algorithm only calculated QTc in 56% of patients.
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