Increased Short-Term Variability of the QT Interval in Professional Soccer Players: Possible Implications for Arrhythmia Prediction

Background: Sudden cardiac death in competitive athletes is rare but it is significantly more frequent than in the normal population. The exact cause is seldom established and is mostly attributed to ventricular fibrillation. Myocardial hypertrophy and slow heart rate, both characteristic changes in top athletes in response to physical conditioning, could be associated with increased propensity for ventricular arrhythmias. We investigated conventional ECG parameters and temporal shortterm beat-to-beat variability of repolarization (STVQT), a presumptive novel parameter for arrhythmia prediction, in professional soccer players. Methods: Five-minute 12-lead electrocardiograms were recorded from professional soccer players (n = 76, all males, age 22.0 +/- 0.61 years) and age-matched healthy volunteers who do not participate in competitive sports (n = 76, all males, age 22.0 +/- 0.54 years). The ECGs were digitized and evaluated off-line. The temporal instability of beat-to-beat heart rate and repolarization were characterized by the calculation of short-term variability of the RR and QT intervals. Results: Heart rate was significantly lower in professional soccer players at rest (61 +/- 1.2 vs. 72 +/- 1.5/min in controls). The QT interval was prolonged in players at rest (419 +/- 3.1 vs. 390 +/- 3.6 in controls, p<0.001). QTc was significantly longer in players compared to controls calculated with Fridericia and Hodges correction formulas. Importantly, STVQT was significantly higher in players both at rest and immediately after the game compared to controls (4.8 +/- 0.14 and 4.3 +/- 0.14 vs. 3.5 +/- 0.10 ms, both p<0.001, respectively). Conclusions: STVQT is significantly higher in professional soccer players compared to age-matched controls, however, further studies are needed to relate this finding to increased arrhythmia propensity in this population.