Heart Rate–Corrected QT and JT Intervals in Electrocardiograms in Physically Fit Students and Student Athletes

Abstract

In literature, data on the prevalence of prolonged and shortened corrected QT (QTc) have shown considerable variability. The aim of the study was to compare QTc and JTc intervals of competitive student athletes and noncompetitive sport participants to QTc cutoff points used in athletes. A group of 485 physically fit candidates for the study of kinesiology (139 female and 346 male candidates) aged 18-20 participated in the study. Basic anthropometry, field fitness test, cardiovascular, electrocardiograms measurements, and blood sampling for lipid profile were conducted. The prolonged QTc according to European Society of Cardiology criteria was found in 2.9% of female and 4.3% of male students. When the "Seattle criteria" were used, the proportion of prolonged QTc was 1.44% in female and 0.29% in male students. The shortened QTc according to the Seattle cutoff points was presented in 0.7% of female and 2.0% of male students. The JTc over 400 ms was found in 0.72% of female and 0.29% of male students. The JTc shorter than 320 ms was presented in 0.7% of female and 1.1% of male students. No significant differences were found between students involved in competitive sport and those involved in recreational sporting activities. Female students had lower body mass index and blood pressure values, better blood lipid profile, and lower uric acid concentrations. In conclusion, the Seattle criteria markedly decreased the proportion of prolonged QTc in student athletes, particularly in male students. It seems that the JTc interval could be a better parameter than the QTc interval for the estimation of specific repolarization time in physically fit university students.

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“…4. 25,26 ECG interval changes from the baseline measurement were assessed using a time-matched analysis as suggested by the International Conference on Harmonization (ICH) E14 guideline. 27,28 The QTc prolongation (ΔQTc), QRS prolongation (ΔQRS), JTc prolongation (ΔJTc), and PR prolongation (ΔPR) were modeled separately.…”

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“…Additionally, this relationship is used for the detection of prolonged repolarization in ventricular conduction defects [ 28 ], but the JT interval is constructed as a linear function of the RR interval in the mentioned study. Similarly, it was shown in [ 29 ] that a heart rate’s corrected JT interval was a good estimate of specific repolarization time in a cohort of physically fit university students. There is a well-known parabolic relationship between the HR and JT interval: when the HR rises, the JT interval shortens, and vice versa.…”

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