title: Changes in QT interval with exercise in elite male rowers and controls.
abstract: BACKGROUND
  QT interval prolongation occurs at rest and during exercise in pathological left ventricular hypertrophy. However, athletes with physiological hypertrophy have normal QT at rest. The aim of this study was to compare the effect of exercise on QT in athletes with echocardiographic left ventricular hypertrophy and normal controls, and explore differences in their response.
  
  
  METHODS
  Elite male rowers (n=15) with echocardiographic left ventricular hypertrophy, and normal volunteers (n=15) underwent 15 min of a Bruce protocol treadmill test. Electrocardiograms (ECGs) were recorded during each stage and every minute during recovery for 3 min. QT was measured at each stage. Corrected QT (QTc) was calculated using Bazett's formula.
  
  
  RESULTS
  QT at rest was significantly greater than QT after 3 min of recovery in the controls (0.36+/-0.02 vs. 0.32+/-0.04 s; P=0.001) but not in the athletes (0.36+/-0.03 vs. 0.34+/-0.02 s; P=0.05). Regression lines for QT versus heart rate showed a strongly negative correlation in both athletes and controls (y=0.463-0.0013x (r=0.91; P<0.0001) and y=0.461-0.0013x (r=0.93; P<0.0001), respectively), but greater individual homogeneity in the athletes.
  
  
  CONCLUSIONS
  training-induced hypertrophy does not affect the heart rate/QT relationship. The more rapid recovery in QT and homogeneity of the heart rate/QT relationship in athletes compared to controls is likely to be a benign effect of myocardial fitness, but it is hypothesised that it may contribute to arrhythmias in the unfit individual after vigorous exertion.
authors.affiliation: Academic Cardiology Unit, St. Mary's Hospital, 10th Floor QEQM Wing, South Wharf Road, Imperial College School of Medicine, W2 1NY, London, UK. kumaran.rajappan@ic.ac.uk
authors.forename: Kim
authors.initials: K
authors.lastname: Rajappan
authors.forename: Clare
authors.initials: C
authors.lastname: O'Connell
authors.forename: Desmond J
authors.initials: DJ
authors.lastname: Sheridan
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004452:Echocardiography; D004562:Electrocardiography; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000175:diagnosis*; D008297:Male; D010807:Physical Endurance; D005082:Physical Exertion / Q000502:physiology*; D011336:Probability; D012016:Reference Values; D018570:Risk Assessment; D013177:Sports / Q000502:physiology*