Read the summary and the most important questions on 12-lead ECG in the athlete: physiological versus pathological abnormalities

• 1 Introduction

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• What are the underlying events that cause early repolarization?

  physiological adaptation of the cardiac autonomic nervous system.
  

  • increased vagal tone
    
  • withdrawal of sympathic activity  
    

• 2 COMMON AND TRAINING-RELATED ECG CHANGES

• In what groups are ECG abnormalities more common?

  • Male
  • African
  • Highly-trained endurance

• Endurance sports can induce adaptive physiological changes of the ECG, what are the most common changes?

  • sinus bradycardia
  • increased QRS-voltage
  • increased LV wall thickness

• 2.1 Sinus bradycardia/arrhythmia

• What is the definition of sinus bradycardia?

  heart rate < 60bpm in rest.

• How does the sinus bradycardia respond to exercise?

  It disappears, as may be explained by the high vagal tone in athletes.

• 2.1.1 Work-up

• How is bradycardia caused in athletes?

  By physiological adaptive change of the autonomic nervous system and reflects the level of athletic conditioning.

• How is physiological sinus bradycardia distinguished from pathological sinus bradycardia?

  1. decrease in heart rate is proportional to level of training
  2. absence of dizziness/syncope
  3. HR becomes normal during exercise and max heart rate is preserved
  4. bradycardia reverses with detraining.

• 2.2 AV block

• How does an AV-block express itself?

  A slowing of the heartrate by a prolonged delay in firing of the AV after receiving input from the sinus.

• How are first degree AV-blocks and second degree Mobitz I blocks recognized in the ECG?

  first degree: Longer P to QRS interval (>0.2s)
  second degree Mobitz I: Longer PR interval and dropped beat, narrow QRS

• What may be a reason for functional AV-block?

  The shift to dominance of the parasympathic autonomic system.