RELATION BETWEEN β- BLOCKING THERAPY AND SYMPTOMS AND QT DISPERSION IN CHILDREN WITH LONG QT SYNDROME
Introduction: QT dispersion (QTd) reflects partial differences in duration of ventricular repolarization. Increased QTd may reflect heart vulnerability to ventricular arrhythmias and is strongly connected with impaired function of autonomic nervous system. There is little data on clinical significance of QTd in children with Long QT Syndrome (LQTS).
Aim: To evaluate the impact of B-blocking therapy (BBT) on QTd and corrected QTd (QTcd) dispersion in symptomatic and asymptomatic children with LQTS.
Methods: The study groups comprised 64 consecutive pediatric patients (33 males), mean age 11.4±4.7 yrs, admitted to the Cardiology Department and diagnosed with LQTS according to Schwartz criteria. QTd and QTcd were measured from 12-lead surface ECG.
Results: 31 patients were symptomatic and out of them 25 had a history of syncope in emotional or physical stress. In 6 children cardiac arrest (CA) was the first manifestation of the disease. There was no difference in QTd and QTcd between asymptomatic and symptomatic children (0.062±0.034 vs. 0.081±0.057; p= 0,13 and 0.070±0.039 vs. 0.082±0.055; p= 0.329, rescpectively). 32 patients were treated with b-blockers (19 symptomatic and 13 asymptomatic). There was no difference in QTd and QTcd between patients on BBT versus untreated (0.067±0.038 vs. 0.076±0.056; p= 0.449 and 0.068±0.034 vs. 0.084±0.057; p= 0,190, respectively).
Conclusions: Our data indicate that in a group of pediatric patients with LQTS, QTd and QTcd do not correlate with symptoms neither are influenced by BBT.