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

## TL;DR

A smartphone app was developed to measure QT intervals from ECG snapshots and was validated for accuracy in adults without heart conditions.

## Contribution

A novel smartphone application for semi-automated QT interval analysis was developed and validated.

## Key findings

- The app showed clinically acceptable agreement for QT interval measurements.
- The app's QTc interval measurements also met clinical acceptability standards.
- Validation was performed on 57 adults without cardiac comorbidities.

## Abstract

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 (QTAPP and QTcAPP; test method) and simultaneously manually measured QT and QTc intervals from a 12-lead ECG (QTREF and QTcREF; reference method) in 57 adult volunteers and patients who had sinus rhythm and no acute or chronic cardiac comorbidities. To investigate the agreement between QTAPP and QTREF and between QTcAPP and QTcREF, 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 QTAPP and QTREF was 14 ± 20 ms (95%-LOA −26 to 54 ms). The mean of the differences between QTcAPP and QTcREF was 13 ± 15 ms (95%-LOA −16 to 42 ms). The agreement between QTAPP and QTREF and between QTcAPP and QTcREF was clinically acceptable in adult volunteers and patients without cardiac comorbidities.

The online version contains supplementary material available at 10.1007/s10877-025-01277-z.