title: Increased short-term variability of the QT interval in professional soccer players: possible implications for arrhythmia prediction.
abstract: 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 short-term beat-to-beat variability of repolarization (STV(QT)), 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, STV(QT) 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
  STV(QT) 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.
authors.affiliation: 1st Department of Internal Medicine, Faculty of Medicine, University of Szeged, Szeged, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Lengyel
authors.forename: Andrea
authors.initials: A
authors.lastname: Orosz
authors.forename: Péter
authors.initials: P
authors.lastname: Hegyi
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Komka
authors.forename: Anna
authors.initials: A
authors.lastname: Udvardy
authors.forename: Edit
authors.initials: E
authors.lastname: Bosnyák
authors.forename: Emese
authors.initials: E
authors.lastname: Trájer
authors.forename: Gábor
authors.initials: G
authors.lastname: Pavlik
authors.forename: Miklós
authors.initials: M
authors.lastname: Tóth
authors.forename: Tibor
authors.initials: T
authors.lastname: Wittmann
authors.forename: Julius Gy
authors.initials: JG
authors.lastname: Papp
authors.forename: András
authors.initials: A
authors.lastname: Varró
authors.forename: István
authors.initials: I
authors.lastname: Baczkó
mesh_terms: D000293:Adolescent; D000328:Adult; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D056352:Athletes; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D012916:Soccer; D013997:Time Factors; D014463:Ultrasonography; D055815:Young Adult