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β-receptor blockers significantly impact the cardiovascular system by counteracting catecholamine-induced sympathetic responses. These medications decrease heart rate, contractility, and cardiac output, potentially leading to cardiac depression, life-threatening bradycardia, and death. Therapeutically, β-blockers function as mild antihypertensives and are utilized in treating angina pectoris and cardiac arrhythmias. However, nonselective β-blockers inhibit β2-receptors in bronchial smooth...
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Beta-Blockers and Exercise Performance in Children with Long QT Syndrome.

Gregory Webster1, Nathan Gill2, Thomas Carberry3

  • 1Division of Cardiology, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.

JACC. Clinical Electrophysiology
|July 10, 2026
PubMed
Summary

Beta-blocker dosage in young patients with long QT syndrome (LQTS) did not impact exercise performance measures like peak oxygen consumption. However, higher doses did linearly affect heart rate response, indicating physiological beta-blocker effects.

Keywords:
beta-adrenergic receptor antagonistcardiopulmonary exercise testelectrophysiologylong QT syndromepediatricpharmacology

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Area of Science:

  • Cardiology
  • Pediatric Electrophysiology
  • Sports Medicine

Background:

  • Young individuals with long QT syndrome (LQTS) often experience concerns regarding exercise capacity while on beta-blocker therapy.
  • Understanding the impact of medication dosage on physical activity is crucial for managing LQTS in pediatric populations.

Purpose of the Study:

  • To investigate the relationship between beta-blocker dosage and objective measures of cardiopulmonary fitness in young patients diagnosed with LQTS.
  • To determine if increasing doses of beta-blockers influence peak oxygen consumption, respiratory exchange ratio, or exercise heart rate response.

Main Methods:

  • A retrospective analysis of treadmill cardiopulmonary exercise tests (CPETs) was conducted on 93 pediatric patients with LQTS.
  • Key metrics including peak oxygen consumption (Vo2), respiratory exchange ratio (RER), blood pressure, and percent predicted heart rate (%PHR) were analyzed.
  • Data from nadolol (non-cardioselective) were primarily analyzed, with atenolol (cardioselective) data used for validation.

Main Results:

  • No correlation was found between nadolol dose and peak oxygen consumption (Vo2) or peak respiratory exchange ratio (RER), indicating preserved aerobic capacity.
  • A significant linear decrease in percent predicted heart rate (%PHR) was observed with increasing nadolol dose, confirming beta-blocker's physiological effect.
  • Mild blood pressure changes and stable peak Vo2 and RER were noted with increased atenolol dosage in the validation cohort.

Conclusions:

  • In pediatric patients with LQTS, higher doses of nadolol do not appear to compromise objective measures of peak exercise performance (peak Vo2, RER).
  • Despite a dose-dependent effect on heart rate (%PHR), nadolol treatment for LQTS is unlikely to significantly impair exercise capacity for most young patients.
  • Findings were consistent with atenolol data, suggesting a generalizable effect of beta-blockers on exercise performance in LQTS management.