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(Circulation. 1972;46:123.)
© 1972 American Heart Association, Inc.

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Demonstration of Entrance Block into the Atrioventricular Node of Man

P. JACOB VARGHESE M.D.¹; ANTHONY N. DAMATO M.D.¹; KAREN L. PAULAY M.D.¹; JOHN J. GALLAGHER M.D.¹; SUN H. LAU M.D.¹

¹ From the Cardiopulmonary Laboratory, U. S. Public Health Service Hospital, Staten Island, New York.

Entrance block of an atrial premature beat (APB) into the atrioventricular node is demonstrated by its lack of effect on the A-V nodal conduction of a subsequent beat which is introduced before the full recovery time of the A-V node. This phenomenon was demonstrated in five patients by using programmed atrial stimulation and His bundle recordings. Entrance block into the A-V node occurred in a narrow range (28-33%) of the basic cycle length and concealed conduction occurred at coupling intervals longer than this range. It appears that entrance block of these early APBs is due to a "functional block" between the atrium and the A-V node. The concept of an entrance block into the A-V node is useful in explaining some forms of the supernormal phase of A-V conduction as well as in the interpretation of complex arrhythmias.

Key Words: Concealed conduction • Full recovery time of A-V node • His bundle recordings • Supernormal phase of A-V conduction • Premature atrial stimulation

Submitted on October 7, 1971
Accepted on February 18, 1972