title: Temporal patterns of progression and regression of electrical and mechanical remodeling of the atrium.
abstract: OBJECTIVE
  We evaluated serial changes of electrical and mechanical parameters of atrial remodeling in dogs subjected to rapid atrial pacing.
  
  
  BACKGROUND
  Prolonged rapid atrial excitation causes electrical and mechanical remodeling, which contributes to persistence of atrial fibrillation and clot formation. However, the temporal relationship between these two types of atrial remodeling remains unknown.
  
  
  METHODS
  In 8 dogs, rapid pacing at 400 ppm was continued for 14 days. The electrophysiologic and transesophageal echocardiographic studies were performed on the day before and after 2, 7, and 14 days of rapid pacing, then 1 and 7 days after the cessation of pacing. These were compared with sham-operated dogs (instrumented but not paced, n=6).
  
  
  RESULTS
  With rapid pacing, there was an immediate shortening of the effective refractory period (ERP) and decreases in the transmitral atrial wave velocity (MAV) and the left atrial appendage emptying velocity (LAAV). In contrast, conduction velocity (CV) decreased and the left atrial appendage area (LAAA) increased progressively over 14 days. During the recovery, ERP, MAV, and LAAV returned to the baseline in 1 day, whereas CV and LAAA did in 7 days. ERP was highly positively correlated with LAAV (r=0.78, p<0.001) and MAV (r=0.73, p<0.001), while CV was negatively correlated only with LAAA (r=-0.58, p<0.001).
  
  
  CONCLUSIONS
  Pacing-induced electrical and mechanical remodeling of the atrium exhibits divergent patterns of progression and regression such that changes of ERP and contractile function take place more rapidly than those of CV and atrial size.
authors.affiliation: Cardiology Division, Department of Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, 160-8582 Tokyo, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Kinebuchi
authors.forename: Hideo
authors.initials: H
authors.lastname: Mitamura
authors.forename: Akiko
authors.initials: A
authors.lastname: Shiroshita-Takeshita
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kurita
authors.forename: Narutaka
authors.initials: N
authors.lastname: Ohashi
authors.forename: Kojiro
authors.initials: K
authors.lastname: Tanimoto
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Fukuda
authors.forename: Masaki
authors.initials: M
authors.lastname: Ieda
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sato
authors.forename: Motoki
authors.initials: M
authors.lastname: Hara
authors.forename: Seiji
authors.initials: S
authors.lastname: Takatsuki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D016275:Atrial Function; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D018450:Disease Progression; D004285:Dogs; D018618:Echocardiography, Doppler, Color; D017548:Echocardiography, Transesophageal; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology; D008297:Male; D008955:Models, Cardiovascular; D012032:Refractory Period, Electrophysiological