Reproducibility of QT Interval Measurements Obtained from 24‐Hour Digitized Ambulatory Three‐Lead Electrocardiograms in Patients with Acute Myocardial Infarction and Healthy Volunteers

Abstract

BackgroundChanges in QT interval durations on 24‐hour ambulatory ECGs reflect circadian variations in ventricular repolarization. However, the reproducibility of such measurements is unknown.MethodsTwo 24‐hour Holter recordings were obtained in 9 healthy volunteers, and in 15 post‐myocardial infarction (Ml) patients. First, automated measurements of QT apex and QT end were compared with manual measurements. Second, automated measurements of QT intervals were compared for each subject between the first and second Holter recordings. The coefficient of reproducibility was calculated as twice the standard deviation of differences between paired measurements.ResultsThe coefficient of reproducibility for the comparison of manual and automated measurements of QT apex was 9 ms in healthy volunteers and 12 ms in post‐MI patients. This coefficient was 12 ms in both healthy volunteers and post‐MI patients for the comparison of manual and automated measurements of QT end. The coefficient of reproducibility for the comparison of automated measures of QT apex in the two Holter recordings was 16 ms in healthy volunteers and 18 ms in post‐MI patients. These coefficients were 19 ms and 23 ms, respectively, for the comparison of automated measures of QT end.ConclusionsAutomated and manual measurements of QT intervals obtained from 24‐hour ambulatory ECGs provide similar results. Short‐term reproducibility of automated measurements of QT intervals is acceptable.