Comparison and recalculation of the very different QTc interval durations in young healthy women

The aim was to use some simple way for easier comparison, other expression or recalculation of the QTc duration from one formula to another in order to remove the large QTc differences.Methods and Results: The QT interval duration in 138 young healthy women was taken from our archive. The measured QT interval was corrected for heart rate (QTc) according to nine published regression equations (Bazett, Fridericia, Hodges, Sarma, Lecocq, Rautaharju, Sagie=Framingham, Arrowood, Malik) and compared mathematically by the Pearson correlation coefficient R and graphically by linear correlation.Correlation between two different QTc durations can be of three kinds: small (e.g. Bazett’s versus Malik’s formulas, R=0.0525, p=0.5405, the QTc values are much dispersed in the graph), larger (Malik’s versus Sarma’s formulas, R=0.939, p<0.01, the values are less dispersed), and identical (the Rautaharju’s versus Arrowood’s formulas, R=1.000, p<0.01, all QTc points are situated on one line). The linear correlation QTc1 = a+b·QTc2 enables recalculation from one QTc formula into another, if necessary.In conclusion, the QTc interval durations are differently long according to the QTc formula used. The correlations with the large Pearson R coefficient indicate the QTc pairs inappropriate for recalculation, the small R values indicate the appropriate pairs for recalculation

Corrected QT interval in white young healthy women: Should the norms be updated?

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

Circa-and ultradians in the occurrence of simple extrasystoles in healthy men at lowland in the light of inferential statistics

Purpose . An exact description of circadian and ultradian rhythms of simple extrasystoles in healthy subjects is lacking. Thirty-seven healthy male subjects, aged 50–76, were randomly taken. Simple extrasystoles from 24-hour Holter ECG were registered and calculated per each hour and processed by cosinor regression. Their occurrence is formulated by 95% confidence and tolerance corridors for supraventricular and ventricular extrasystoles. Results . The number of extrasystoles is relatively low, dispersion of ventricular extrasystoles is significantly higher than supraventricular ones. A significant increase of their frequency versus the general zero trend straight line was found only around 9 a.m. In supraventricular ones a significant increase around 6–7 a.m., 9 a.m., noon, and 4–5 p.m. and a significant depression around 1–2 a.m. and 10 p.m. was present. Only the 24-hour rhythm is significantly present (α=0.05) in ventricular beats while in supraventricular ones also the period lengths of 12, 6, 4, 3.4 and 2.4 hours are significant. The significant difference between supraventricular and ventricular extrasystoles exists in the 24-hour amplitudes and 6-hour acrophases. Conclusion . One circadian and several ultradian rhythms of simple extrasystoles are present in healthy male subjects over 50 years of age. The 95% tolerance chronograms can be exploited in clinical practice