Functional Properties of the Atrioventricular Conduction System.

• The nature of the system responsible for transmission of excitation from atria to ventricles of the mammalian heart has been a recurrent problem in pl^siology. In 1910 Erlanger demonstrated conclusively that the only normal functional connection between these chambers is the specialized tissue of the bundle of His. However, anatomical evidence showing the occasional presence of other connections composed of muscular tissue has been provided by the studies of Kent, Lev, and Truex, among others. The syndrome described by Wolff et al. suggested that anomalous atrioventricular excitation might result from the spread of activity over pathways which were anatomically distinct from the atrioventricular node and bundle of His. Quite recently James demonstrated several tracts of fibers in human hearts which bypass the A-V node and which thus might establish functional A-V connections. In 1956 Moe made a detailed and exhaustive analysis of the spread of premature impulses from the atria to ventricles and in the opposite direction. On the basis of this analysis he postulated the existence of a dual A-V transmission system in which two groups of fibers differed with respect to duration of refractoriness and