title: Atrioventricular node functional remodeling induced by atrial fibrillation.
abstract: BACKGROUND
  The atrioventricular node (AVN) plays a vital role in determining the ventricular rate during atrial fibrillation (AF). AF results in profound electrophysiological and structural remodeling in the atria as well as the sinus node. However, it is unknown whether AVN undergoes remodeling during AF.
  
  
  OBJECTIVE
  To determine whether AVN undergoes functional remodeling during AF.
  
  
  METHODS
  AVN conduction properties were studied in vitro in 9 rabbits with AF and 10 normal controls. A previously validated index of AVN dual-pathway electrophysiology, His-electrogram alternans, was used to monitor fast-pathway or slow-pathway (SP) AVN conduction in these experiments. AVN conduction properties were further studied in vivo in 7 dogs with chronic AF and 8 controls.
  
  
  RESULTS
  Compared with the control rabbits, the rabbits with AF had a longer AVN conduction time (83 ± 16 ms vs 68 ± 7 ms; P <.01), longer AVN effective refractory period (141 ± 27 ms vs 100 ± 9 ms; P <.01), an earlier transition from fast-pathway to SP conduction (at a longer prematurity, 249 ± 60 ms vs 171 ± 24 ms; P <.01), and a slower ventricular rate during simulated AF (RR interval 249 ± 42 ms vs 202 ± 12 ms; P <.01). Notably, a larger proportion of conducted beats utilized the SP in AF preparations (92% ± 12% vs 63% ± 32%; P <.05). Long-term AF in dogs resulted in a longer atrioventricular conduction time and AVN effective refractory period and a slower ventricular rate during AF compared with the controls.
  
  
  CONCLUSIONS
  Pronounced AVN functional electrophysiological remodeling occurs after long-term AF, which could lead to a spontaneous slowing of the ventricular rate. Furthermore, the SP dominance during AF underscores the effectiveness of its modification by ablation for ventricular rate control during AF.
authors.affiliation: Department of Cardiovascular Medicine and Molecular Cardiology, Cleveland Clinic, Cleveland, Ohio, USA. yzhang49@nyit.edu
authors.forename: Youhua
authors.initials: Y
authors.lastname: Zhang
authors.forename: Todor N
authors.initials: TN
authors.lastname: Mazgalev
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000150:complications / Q000473:pathology*; D001283:Atrioventricular Node / Q000473:pathology*; D002304:Cardiac Pacing, Artificial; D004285:Dogs; D004562:Electrocardiography; D006329:Heart Conduction System; D006339:Heart Rate; D066298:In Vitro Techniques; D011817:Rabbits; D013997:Time Factors; D020257:Ventricular Remodeling