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Corrected QT interval in white young healthy women: should the norms be updated?
1P. J. Šafárik University Department of Medical Physiology, Faculty of Medicine Košice Slovak Republic.
Abstract:
The electrocardiographic QT interval duration is a frequently studied ECG parameter. The aim of this study was to compare the quantitative influence of nine QTc formulae and discuss the duration of QT/QTc normal values. The QTc duration was calculated from manually measured QT intervals and heart rate of the Frank XYZ electrocardiograms in 138 white young healthy Slovak women (18-24 years, 690 primary ECG measurements). Dispersion of the QT/QTc interval values was not Gaussian (Shapiro-Wilk test) in most cases. The course of the measured QT regression lines were -1.9186 HR + 511.13 ms or 0.1504RR + 245.72 ms. Median QTc duration in ms was decreasing in this sequence: Bazett 407.04, Fridericia 394.61, Hodges 393.27, Rautaharju and Arrowood 368.79, Framingham-Sagie 368.78, Lecocq 368.70, Sarma 368.66, and Malik 338.70. No QTc value above 440 ms was found after Hodges' correction only. The differences of median QTc values were significant (P < 0.01) in most possible combinations (Kruskal-Wallis test). We recommend using the QTc formula created from observed persons only and updating the QT interval norms. So-called "ideal" QTc models from other not examined persons are methodically incorrect and may produce the misleading results. The frequently used Bazett formula is appropriate for orientation only.
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