Unexpected Total Preexcitation Possibly Secondary to Pseudoblock

Abstract

The term, atrioventricular (AV) block, has been used to characterize a phenomenon in which blocked P waves reflect the occurrence of concealed junctional or fascicular extrasystoles.14 The mechanism of pseudo AV block is concealed conduction of the electrocardiographically silent extrasystole to the AV node, resulting in block of the subsequent P wave. In the present report, we describe a patient with preexcitation who manifested fusion complexes of normal and anomalous pathway conduction during sinus rhythm, and also sporadic QRS complexes with unexpected total preexcitation. The occurrence of junctional extrasystoles in this patient suggested that pseudoblock of the normal AV pathway produced the unexpected beats with total preexcitation.