Electrophysiologic effects of disopyramide in children.

Disopyramide has been successfully used to treat a variety of supraventricular and ventricular arrhythmias. The electrophysiologic effects of this drug were studied following diagnostic cardiac catheterization in 14 children aged 7 months to 14 years, suffering from congential heart disease. Surface EKG, intra-atrial, and His bundle electrogram as well as right atrial pacing with the use of extrastimulus technique were obtained before and after a single intravenous dose of disopyramide (2 mg/Kg, max 50 mg). The drug significantly prolonged the HV interval, effective and functional refractory periods of the atrium and the AV node. The most consistent change was the prolongation of the atrial refractory periods. The electrophysiologic effects of this drug on the conduction system have been variable and this variability has been attributed to the degree of vagal tone. The findings in this age group are similar to adults with simultaneous cholinergic blockade. This might be due to the direct depressant effects of disopyramide on the atrial and AV nodal tissue, and point to the potential usefulness of this drug in the pediatric age group.