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Dynamics of the QT interval during and after exercise in healthy children

M Viitasalo1, L Rovamo, L Toivonen

  • 1Department of Medicine, Helsinki University Central Hospital, Finland.

European Heart Journal
|November 1, 1996
PubMed

Insights

The QT interval

Area of Science:

  • Pediatric Cardiology
  • Electrophysiology
  • Exercise Physiology

Background:

  • QT interval dynamics and homogeneity are key indicators of ventricular arrhythmia susceptibility.
  • Accurate assessment of repolarization is crucial in pediatric exercise testing.

Purpose of the Study:

  • To investigate the relationship between QT intervals (early, total, and late) and heart rate during exercise and recovery in healthy children.
  • To compare the linearity of QT interval correlations with heart rate versus cardiac cycle length.
  • To evaluate the impact of different rate correction methods on QT interval assessment.

Main Methods:

  • Measured early, total, and late QT intervals in 18 healthy children across a range of heart rates (60-180 bpm).
  • Analyzed QT intervals during graded exercise and subsequent recovery phases.
  • Compared linear correction methods with Bazett's method for rate correction.

Main Results:

  • Total QT and early QT showed strong linear correlations with heart rate (r > 0.99).
  • The QT interval's relationship with heart rate differed significantly between exercise and recovery phases.
  • Repolarization inhomogeneity (late QT) increased at higher heart rates.
  • Bazett's method yielded abnormal QT intervals in 67% of children, unlike linear correction.

Conclusions:

  • The QT interval-heart rate relationship is linear but distinct during exercise and recovery in children.
  • Repolarization inhomogeneity rises with increasing heart rate during exercise.
  • Linear correction of QT intervals offers a more accurate assessment during pediatric exercise testing compared to Bazett's method.

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