Concealed re-entry in the human heart.

The mechanism and electrophysiologic manifestations of concealed re-entry were studied in human electrocardiograms and intracardiac recordings. Previously described patterns of concealed re-entry were documented in 49 patients. In seven cases concealed re-entry was involved in the genesis of Wenckebach periodicity and alternating Wenckebach periodicity in the AV node, and "reversed" Wenckebach periods in the His-Purkinje system. These manifestations of concealed re-entry were not described so far. In five cases re-entry was apparently concealed. Complete (but hidden) circus movement of the supraventricular impulses in these patients were detected by intracardiac recordings and by analysing the effects of echo beats on timing of the subsequent sinus beats. Concealed re-entry of the cardiac impulse is a well-documented electrophysiologic event which explains many common and peculiar manifestations of impulse formation and impulse conduction in the human heart.