QT dynamics evaluated on fully automated QT measurement in children.

Abstract

The association between QT interval and heart rate (HR), QT dynamics, has been reported to vary greatly between individuals. We investigated QT dynamics using fully automated QT interval measurement with a commercially available multifunctional electrocardiogram (ECG) recorder. The study group included 17 otherwise healthy subjects (mean age, 12.7 years; 11 girls, 6 boys), who were undergoing exercise test for arrhythmia evaluation. The subjects had single premature ventricular contraction. Mean corrected QT interval (Fridericia) at rest was 412 ± 19 ms (male, 408 ± 20 ms; female, 414 ± 19 ms), manually measured with a digitizer, using the tangent method. We assessed QT interval/HR slope during the whole exercise test, the exercise phase, and the recovery from exercise phase; the slopes were calculated offline after excluding wide QRS complex and were -1.15 ± 0.26 (r(2) = 0.65), -1.18 ± 0.30 (r(2) = 0.62), and -1.11 ± 0.25 (r(2) = 0.70), respectively. Estimated QT interval at HR 60 beats/min (QT60) was calculated using the regression line formula and was 383 ± 24 ms, 387 ± 28 ms, and 375 ± 21 ms, respectively. QT60 of the total exercise test correlated with the corrected QT interval at rest (P = 0.04, r(2) = 0.25). Assessment of QT dynamics is feasible on fully automated QT interval measurement with this ECG recorder. Further studies are required in larger populations to confirm the accuracy and precision of QT measurement and QT dynamics using this new multifunctional ECG.