Key result
Beta-blocker therapy linked to ~15% QTc reduction during face immersion in pediatric long QT syndrome.
Why the study?
Does the interval from the nadir of the notch to the end of the T wave represent transmural dispersion of repolarization in children and adolescents with congenital long QT syndrome?
Observational (n=36)
No
Does the interval from the nadir of the notch to the end of the T wave represent transmural dispersion of repolarization in children and adolescents with congenital long QT syndrome?
Absolute Event Rate: 0.428% vs 0.504%
p-value: p=0.0431
The interval from the nadir of the notch to the end of the T wave on surface ECG represents transmural dispersion of repolarization in children and adolescents with long QT syndrome.
Beta-blockers were associated with shorter QTc during immersion testing in pediatric LQTS; leaves open confirmation in larger prospective studies.
BACKGROUND: It has been shown experimentally that the interval from the nadir of the initial negative T wave to the end of the T wave is representative of transmural dispersion of repolarization (TDR) when complex T waves are present. In the clinical setting, however, the interval representative of TDR in patients with long QT syndrome (LQTS) is a controversial subject. METHODS AND RESULTS: Five symptomatic patients (3 boys, 2 girls; 3 LQT1, 2 LQT2) were evaluated by a face immersion test before and after treatment to compare the configuration of the T wave. When the notch disappeared after treatment, the single peak of the T wave after treatment coincided with the nadir of the notch before treatment. When the notch remained the same after treatment as before treatment and when the QTc decreased, the corrected interval from the nadir of the notch to the end of the T wave was for the most part shortened. CONCLUSIONS: The present study showed that the interval representative of the TDR in the clinical surface electrocardiogram can be obtained from the nadir of the notch to the end of the T wave in children and adolescents with LQTS, as was shown in the experimental study.
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Haraguchi et al. (2004) conducted an observational in Congenital Long QT Syndrome (n=36). Beta-blocker treatment vs. Pre-treatment baseline was evaluated on Mean QTc value during face immersion test at minimal heart rate (p=0.0431). Beta-blocker treatment significantly decreased the mean QTc interval during a face immersion test from 0.504 to 0.428 s1/2 (p=0.0431) in children and adolescents with congenital long QT syndrome.
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