Abstract 17394: Measurement of Corrected QT Interval on Apple Watch Series 4 Electrocardiogram Has Moderate to Strong Agreement with 12-Lead Electrocardiogram

Introduction: The Apple Watch Series 4 (AW) has native hardware to measure a single-lead ECG (corresponding to Lead I) and detect atrial fibrillation. Wearable technology is an attractive area of research for its screening, monitoring, and diagnostic capabilities. One utility is the convenient ambulatory monitoring of the corrected QT (QTc) for pathophysiologic or pharmacologic reasons. The objective of this study was to compare measurements of the QTc on the AW with Leads I, II, and III of a 12-lead ECG. Methods: AW and 12-lead ECGs were obtained on healthy volunteers age > 18 years at a university hospital. QT intervals and RR intervals were manually measured with calipers to the nearest 0.25 millimeter on standard ECG paper for both devices. Bland-Altman plots were used to assess the level of agreement between QTc measurements on the AW and 12-lead ECGs. Strong and moderate agreement was defined as < 20 and < 40 milliseconds (ms), respectively, away from the mean difference of the sample. Results: Waveforms on the AW ECGs (n=63) and Leads I (n=41), II (n=42), and III (n=39) of the 12-lead ECGs from 20 volunteers (mean age 32 years, 70% female) at a university hospital were analyzed. Six volunteers had sinus bradycardia with mean heart rate (HR) of 55 bpm. No arrhythmias were noted, and none of the volunteers were on antiarrhythmic or QT-prolonging medications. The mean HR was 69 ± 11 bpm on AW and 67 ± 10 bpm on 12-lead ECG. For QTc measurements on AW compared to 12-lead ECG, the mean difference was -13.71 ± 27 ms for Lead I, -11.27 ± 24 ms for Lead II, and -10.38 ± 24 ms for Lead III. Moderate agreement of < 40 ms existed in 56/62 (90%) of QTc measurement comparisons: 18/21 (85.7%) Lead I, 19/21 (90.5%) Lead II, and 19/20 (95%) Lead III. Strong agreement of < 20 ms existed in 32/62 (51.6%) of QTc measurement comparisons: 9/21 (42.9%) Lead I, 13/21 (61.9%) Lead II, and 10/20 (50%) Lead III. Conclusions: Moderate to strong agreement of QTc measurements exists between the AW and Leads I, II and III of a 12-lead ECG.