title: Preceding His-atrial interval as a determinant of atrioventricular nodal conduction time in the human and rabbit heart.
abstract: This investigation shows that atrioventricular (A-V) nodal conduction time (A-H interval), both in the human and in the isolated rabbit heart, is determined mainly by the length of the preceding His-atrial (H-A) interval. The A-H intervals obtained during atrial extrasystolic stimulation at different basic rates, during Wenckebach cycles and during both transient and steady state responses to stepwise increases in stimulation frequency were plotted against the corresponding H-A intervals. The A-H intervals were found to have nearly the same duration provided they were preceded by the same H-A interval. The only important difference appeared in the short H-A interval range as a shortening of the A-H interval at faster basic rates. This facilitating effect of frequency, which was found in the majority of cases, is compatible with the similarly frequency-dependent shortening of the functional refractory period of the A-V node.
mesh_terms: D000818:Animals; D001283:Atrioventricular Node / Q000502:physiology; D002036:Bundle of His / Q000502:physiology; D004558:Electric Stimulation; D004562:Electrocardiography; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D011817:Rabbits