Supernormal conductionがみられた第II度HVブロックの1例

A case of true supernormal AV conduction in the presence of advanced AV block

　Supernormal conductionとは予想されるよりも良い伝導あるいはブロックが予想される時に生ずる伝導を意味する^1）。Supernormal conduction and excitabilityは実験的には証明されているが^2），臨床心電図学上は真のSupernormal conductionの存在は充分に証明されておらず，その多くは既存の電気生理学的機序で証明され"Pseudo-supernormal"と呼ばれている^3,4）。著者らは今回，真のsupernormal現象に基づくと思われるHV伝導におけるsupernormal conductionの1例を経験したので報告する。

A case of true supernormal conduction is described in a patient with advanced AV block. The His bundle recordings demonstrated the site of the AV block to be distal to the His bundle recording site. A. slight slowing of the sinus rate (HH inter-vals between 758 and 840 msec) resulted in tran-sient periods of 1: 1 AV conduction with RBBB, whereas a slight acceleration (HH intervals betwe-en 620 and 760 msec) resulted in 2 : 1 AV block. During premature atrial beats, AV conduction again succeeded at HH intervals between 458 and 598 msec. These findings documented the occurence of supernormal HV conduction at HH intervals of 458 to 598 msec and a refractory period lasting 758-760 msec.