"Supernormal" phase of atrioventricular conduction with concealed capture beats. Significance of odd numbers of P waves between capture beats.

In 1968 Moe and associates postulated multilevel atrioventricular (A-V) block as a mechanism for some forms of the supernormal phase of A-V conduction. In 1971 Schamroth further postulated that, if this were correct, there would only be odd numbers of sinus P waves between the capturing impulses. This report presents two cases of sinus rhythm dissociated from idionodal escape rhythm as a result of high grade A-V block. The rhythm is complicated by manifest and concealed A-V captures during the so-called supernormal phase. There are only odd numbers of P waves between the capturing impulses.