title: Effect of site, summation and asynchronism of inputs on atrioventricular nodal conduction and refractoriness.
abstract: The impulses coming from the sinus node synchronically penetrate the AV node via the crista terminalis and inter-atrial septum. Studies in superfused rabbit AV preparations suggest that the crista terminalis is a more effective input than the inter-atrial septum, and that the summation of both inputs facilitates AV nodal conduction. The aim of this study was to verify the hypothesis in a more physiological model, such as the whole rabbit heart perfused by a Langendorff system. Fifteen rabbit hearts were studied in a Langendorff perfusion system with six bipolar extracellular electrodes: two for stimulating (crista terminalis and inter-atrial septum) and four for recording (crista terminalis, inter-atrial septum, His bundle electrogram and right ventricle). Seven hearts (Group I) were consecutively paced at the crista terminalis, inter-atrial septum and both sites simultaneously, to determine the AV nodal Wenckebach cycle length and effective refractory period under basal conditions and after acetylcholine (0.75 x 10(-6) M). In eight hearts under 0.75 x 10(-6) M acetylcholine (Group II), the crista terminalis and inter-atrial septum were simultaneously (delay = 0 ms) or sequentially (delay = 2, 4, 6, 8, 10, 12, 14, and 16 ms) stimulated to calculate the AV nodal effective refractory period and the AH interval at an atrial coupling interval 5 ms longer than the AV nodal effective refractory period, for each delay tested.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Servei de Cardiologia, Hospital Clinic i Universitari, València, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Sanchis
authors.forename: F J
authors.initials: FJ
authors.lastname: Chorro
authors.forename: L
authors.initials: L
authors.lastname: Such
authors.forename: J
authors.initials: J
authors.lastname: Matamoros
authors.forename: J V
authors.initials: JV
authors.lastname: Monmeneu
authors.forename: J
authors.initials: J
authors.lastname: Cortina
authors.forename: V
authors.initials: V
authors.lastname: López Merino
mesh_terms: D000818:Animals; D016275:Atrial Function; D001283:Atrioventricular Node / Q000502:physiology*; D002036:Bundle of His / Q000502:physiology; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D006346:Heart Septum / Q000502:physiology; D010477:Perfusion; D011817:Rabbits; D012849:Sinoatrial Node / Q000502:physiology