Intrinsic sinus and atrioventricular node electrophysiologic adaptations in endurance athletes

J Am Coll Cardiol. 2002 Mar 20;39(6):1033-8. doi: 10.1016/s0735-1097(02)01722-9.


Objectives: In the present study, we evaluated sinus and atrioventricular (AV) node electrophysiology of endurance athletes and untrained individuals before and after autonomic pharmacologic blockade.

Background: Endurance athletes present a higher prevalence of sinus bradycardia and AV conduction abnormalities, as compared with untrained individuals. Previous data from our laboratory suggest that nonautonomic factors may be responsible for the longer AV node refractory period found in well-trained athletes.

Methods: Six aerobically trained male athletes and six healthy male individuals with similar ages and normal rest electrocardiograms were studied. Maximal oxygen uptake (O(2)max) was measured by cardiopulmonary testing. The sinus cycle length (SCL), AV conduction intervals, sinus node recovery time (SNRT), Wenckebach cycle (WC) and anterograde effective refractory period (ERP) of the AV node were evaluated by invasive electrophysiologic studies at baseline, after intravenous atropine (0.04 mg/kg) and after addition of intravenous propranolol (0.2 mg/kg).

Results: Athletes had a significantly higher O(2)max as compared with untrained individuals. The SCL was longer in athletes at baseline, after atropine and after the addition of propranolol for double-autonomic blockade. The mean maximal SNRT/SCL was longer in athletes after atropine and after propranolol. The WC and anterograde ERP of the AV node were longer in athletes at baseline, after atropine and after propranolol.

Conclusions: Under double-pharmacologic blockade, we demonstrated that sinus automaticity and AV node conduction changes of endurance athletes are related to intrinsic physiology and not to autonomic influences.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / drug effects
  • Adaptation, Physiological / physiology*
  • Adrenergic beta-Antagonists / administration & dosage
  • Adult
  • Atrioventricular Node / drug effects
  • Atrioventricular Node / physiology*
  • Atropine / administration & dosage
  • Electrocardiography
  • Electrophysiologic Techniques, Cardiac
  • Heart Rate / drug effects
  • Heart Rate / physiology
  • Humans
  • Male
  • Parasympatholytics / administration & dosage
  • Physical Endurance / drug effects
  • Physical Endurance / physiology*
  • Propranolol / administration & dosage
  • Reference Values
  • Sick Sinus Syndrome / drug therapy
  • Sick Sinus Syndrome / physiopathology*
  • Sports*
  • Time Factors


  • Adrenergic beta-Antagonists
  • Parasympatholytics
  • Atropine
  • Propranolol