Incessant dual supraventricular tachycardia in a child.

A 5-year-old boy was studied because of incessant supraventricular tachycardia. He was shown to have two forms of supraventricular tachycardia each of which could be incessant. The interplay between the two tachycardias caused interesting periodic sequences in the surface electrocardiogram. Our study illustrates the value of careful analysis of the surface P wave morphology and the usefulness of programmed electrical stimulation of the heart in determining the mechanism of tachycardia.