Electrophysiologic and pharmacologic characteristics of automatic ectopic atrial tachycardia.

In seven children six weeks to nine years of age, the diagnosis of chronic atrial tachycardia due to an automatic ectopic focus was established by clinical course, by the recording of intracardiac electrograms, and by atrial stimulation during cardiac catheterization. Both overdrive atrial pacing and programmed premature atrial stimulation failed to influence the tachycardia. Digoxin reestablished sinus rhythm in one patient while it slowed the tachy- cardia rate slightly in six. Propranolol with digoxin was effective in restoring sinus rhythm in three cases, ineffective in one, and slowed the rate in two. Diphenylhydantoin was effective in one of two patients in whom it was used. Reserpine restored sinus rhythm in the one patient to whom it was given. Although automatic ectopic atrial tachycardias are difficult to manage, an aggressive diagnostic and pharmacologic program results in a high degree of control.