Fig. 2.

Left panel: Scatter plots showing QTc intervals as measured by Apple Watch ECG (awECG-QTc) and standard ECG (sECG-QTc) in leads I, II and V5 (solid circles, subjects with congenital long QT syndrome, open circles, subjects without congenital long QT syndrome). Right panel: Bland-Altman plots showing reproducibility of measuring QTc interval by Apple Watch ECG and standard ECG in leads I, II and V5. The x-axis is the average of the awECG-QTc and sECG-QTc intervals, while the y-axis is the difference between awECG-QTc and sECG-QTc intervals. Solid circles are subjects with congenital long QT syndrome, and open circles are subjects without congenital long QT syndrome.