A computer model for Atrio-Ventricular blocks

Abstract

A mathematical model of the A-V node and of the His bundle has been incorporated into a model of electrical cardiac activity to devise a mechanism for A-V block. A coefficient of conduction efficiency η has been defined whose magnitude can vary from 1-0. Seven theorems are demonstrated which may be summarized as follows: there exist three critical values of η ordered as 1 > η 1 > η 2 > η 3 > 0 such that a first degree block occurs when 1 > η ⩾ η 1, Wenckebach cycles when η 1 > η ⩾ η 2, n:1 block when η 2 > η ⩾ η 3, third degree block when η 3 > η ⩾ 0. A least upper bound is given for the number of consecutive ventricular beats in the Wenckebach phenomenon. Wenckebach cycles are shown to have P-R growth at a decreasing rate and ventricular beat acceleration as the dropped beat is approached, and where n:1 block is interpersed with ( n + 1):1 block, the P-R interval is shorter after n + 1, than after n dropped ventricular beats. Finally, when partial block occurs in the His bundle, a Mobitz II block results. All this corresponds to clinical experience.