Semiautomated QT interval measurement in electrocardiograms from a thorough QT study: comparison of the grouped and ungrouped superimposed median beat methods
Journal of Electrocardiology, 04/25/2012

Hingorani P et al. – Mean QT was 4 milliseconds longer, and interreader variability, 1 millisecond lower with uSMB. Otherwise, both methods were comparable and detected the moxifloxacin effect.

• Three readers manually adjudicated annotations placed by an automated algorithm, using grouped (gSMB) and ungrouped (uSMB) methods in 2658 electrocardiograms (ECGs) recorded in 38 subjects in a crossover design thorough QT study at predose and 6 time points postdosing with placebo or moxifloxacin.

• Placebo–subtracted, moxifloxacin–induced QTcF prolongation was comparable with both methods.
• Maximum QTcF prolongation was seen at 2 hours–10.5 milliseconds (90% confidence interval, 7.9–13.1 milliseconds) with gSMB and 12.9 milliseconds (90% confidence interval, 9.9–15.8 milliseconds) by uSMB.
• Both methods showed good agreement; mean QT was 4 milliseconds greater by uSMB.
• Interreader variability of absolute differences in QT measurements was 1 millisecond lower with the uSMB method (6.8 ± 5.7 milliseconds by gSMB and 5.9 ± 4.5 milliseconds by uSMB).