Wolff-Parkinson-White syndrome. Circus movement tachycardia dependent on procainamide.

A patient with Wolff-Parkinson-White syndrome was disabled by rapid ventricular rates during atrial arrhythmia and by periods of asystole. Circus tachycardia was induced by atrial stimulation only after the administration of procainamide. Nevertheless, treatment with this drug controlled the ventricular rate and spontaneous circus tachycardia did not occur.