Study of retrograde conduction in complete heart block using His bundle recordings.

no H potential or by a prolonged AH interval, indicating concealed retrograde penetration of the His bundle. Thefact that retrograde conductionaffectedanterograde conduction indicates that the anterogradeandretrograde pathways are not totally independent. Atropine significantly improved retrograde conduction; this suggests that the retrograde conduction occurs through the conduction system in a retrograde fashion rather than through a muscular pathway, bypassing a blocked area of the conduction system, as the latter should not be affected by atropine.