Abstract

The aim of this study was to compare three correction methods of QT interval in African national level football players. QT interval was measured in D2 lead on resting electrocardiogram (ECG) in 216 Black male football players (age range 18 to 35 years). Corrected QT (QTc) was calculated using Bazett, Fridericia, and Framingham’s formulas. Means and percentages of long QT (QTc>440 ms and QTc≥470 ms) and short QT (QTc≤320 ms) were compared. Correlations and agreement criteria between correction methods were researched, and effects size were calculated. Heart rate was 59±9 beats/min (40 to 84) and measured QT (QTm) at 383.1±31.4 ms (320 to 480). QTc were 378.9±25.7, 380.1±23.8, and 383.1 ± 31.3 respectively with Bazett, Fridericia, and Framingham formulas; differences were not significant. According to the definition QTc>440 ms, no long QT was found using Fridericia formula whereas Bazett and Framingham showed 1.4% of long QT. Only Framingham’s formula showed long QT according to the definition QTc≥470 ms (0.9%). Framingham’s formula also showed significant difference with short QT as compared to the other methods (5.1 vs. 0.46%; p=0.008). The lower QTc value was 320 ms in all methods. Correlation and agreement were better between Bazett’s and Fridericia’s formula. Framingham’s formula showed higher proportions of long and short QT, while Fridericia’s one reduced them. Bazett's formula gave intermediate percentages. QTcË‚320 ms could be used to define short QT; 320 ms representing the lower limit in our study for the 3 formulas. Our data did not allow us to deduce a definition for the long QT. The limits of QTc ≥ 470 ms for men and QTc ≥ 480 ms for women, more adopted now in the literature, were suggested.

Key words: QT interval, electrocardiogram, football player, Bazett, Fridericia, Framingham.