A smartphone application for semi-automated QT interval analysis based on a snapshot of an electrocardiogram trace displayed on a patient monitor.

We developed a smartphone application (SMART-QT application) that can semi-automatically measure QT and QTc intervals based on a snapshot of the electrocardiogram (ECG) trace and the heart rate displayed on a patient monitor. In this study, we aimed to validate the SMART-QT application. In this prospective single-center method comparison study, we measured QT and QTc intervals with the SMART-QT application (QT and QTc; test method) and simultaneously manually measured QT and QTc intervals from a 12-lead ECG (QT and QTc; reference method) in 57 adult volunteers and patients who had sinus rhythm and no acute or chronic cardiac comorbidities. To investigate the agreement between QT and QT and between QTc and QTc, we performed Bland-Altman analyses and calculated the mean of the differences, the standard deviation, and the 95%-limits of agreement (95%-LOA). We defined clinically acceptable agreement as maximum mean of the differences ± standard deviation of 20 ± 20 ms. The mean of the differences between QT and QT was 14 ± 20 ms (95%-LOA -26 to 54 ms). The mean of the differences between QTc and QTc was 13 ± 15 ms (95%-LOA -16 to 42 ms). The agreement between QT and QT and between QTc and QTc was clinically acceptable in adult volunteers and patients without cardiac comorbidities.