Acute pharmacologic testing of incessant supraventricular tachycardia in a child.

A 3 1/2-year-old child with incessant supraventricular tachycardia was investigated with intravenous vago-mimetic drugs, which had unexpected beneficial results. These observations suggested selection of digitalis as the antiarrhythmic drug, which would not otherwise have been chosen. The potential advantages of non-invasive, acute autonomic modulation for optimal drug selection in children with arrhythmias are illustrated by this case.