A CASE OF SEPTAL WOLFF-PARKINSON-WHITE SYNDROME-ASSOCIATED WITH NEWLYDEVELOPED DELTA WAVES DUE TO DISAPPEARANCE OF IMPEDANCE MISMATCH

A 65-year-old woman who had shown no delta waves or atrioventricular b lock when seen in February 1989, suddenly developed advanced atriovent ricular block in April 1990. The first electrophysiologic study reveal ed that atrioventricular block was caused by His ventricular block, an d only weak retrograde conduction was documented. A DDD-type permanent pacemaker was implanted. One month after implantation, delta waves de veloped. The second electrophysiologic study, performed in February 19 93, disclosed that a Kent bundle with bidirectional conduction capacit y was located at the posterior septum and that the normal conduction s ystem remained blocked at the His ventricular site. The etiology of th e newly developed delta waves seems to be the disappearance of impedan ce mismatch at the ventricular insertion site of the Kent bundle.