Purpose: In the present study we investigated ECG repolarization parameters, including QT variability in young athletes.
Methods: 105 professional athletes (age: 24±5 years) and 105 age-matched healthy volunteers who do not participate in competitive sports (age: 26±10 years) were enrolled in the study. Five-minute 12-lead resting electrocardiograms were recorded before and after treadmill exercise testing, the ECGs were digitized and evaluated off-line using the Cardiosys-A01 system. The following parameters were determined: the frequency corrected QT interval (QTc), QT dispersion (QTd), T wave peak-to-end distance (Tpeak-Tend). Among QT variability parameters we analyzed the QT variance normalized for QT mean, the QT variability index, the short-term beat-to-beat QT interval variability (STV-QT) and the long-term QT variability parameters based on constructed Poincaré plots.
Results: Heart rate was significantly lower in professional athletes at rest (61±10 vs. 71±12/min in controls, p?0.0001). The QT interval was prolonged in athletes at rest (423±32 vs. 390±33 ms in controls, p?0.0001). QTc was significantly longer in athletes before and after treadmill exercise testing compared to controls calculated with Framingham, Fridericia and Hodges correction formulas. However, the QTd (38±13 before and 36±11 ms after exercise vs. 35±11 ms in controls), Tpeak-Tend intervals at rest (96±13 vs. 99±24 ms in controls) did not differ significantly. Importantly, STV-QT was significantly higher in athletes both at rest and following treadmill exercise testing compared to controls (4.29±1.2 and 3.77±1.1 vs. 3.39±0.8 ms, both p?0.01, respectively).
Conclusion: Some of the alterations in repolarization parameters and the significant increase in STV-QT may indicate increased repolarization instability in competitive athletes compared to age-matched controls, however, further studies are needed to relate this finding to increased arrhythmia propensity in this population.