Key result
Isoproterenol alters RR, QT, and QTc similarly in syncope children regardless of coexisting ventricular arrhythmias.
Why the study?
Does beta-adrenergic stimulation with isoproterenol differentially affect QT and QTc intervals in syncope children with versus without coexisting ventricular arrhythmias?
Observational (n=24)
Yes
Does beta-adrenergic stimulation with isoproterenol differentially affect QT and QTc intervals in syncope children with versus without coexisting ventricular arrhythmias?
Beta-adrenergic stimulation with isoproterenol prolongs the QTc interval similarly in children with syncope regardless of the presence of coexisting ventricular arrhythmias.
Isoproterenol prolongs QTc similarly regardless of coexisting arrhythmias; leaves open implications for pediatric syncope risk stratification.
We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.
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Huh et al. (2003) conducted an observational in Syncope or presyncope (n=24). Isoproterenol vs. Syncope only group (vs Ventricular Arrhythmia group) was evaluated on Change in QTc interval in response to isoproterenol between groups (p=>0.05). Beta-adrenergic stimulation with isoproterenol shortened RR and QT intervals and prolonged QTc intervals similarly in syncope children with and without coexisting ventricular arrhythmias.
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