title: Age-related increase in atrial fibrillation induced by transvenous catheter-based atrial burst pacing: an in vivo rat model of inducible atrial fibrillation.
abstract: BACKGROUND
  Large animal models of atrial fibrillation (AF) are well established, but limited experimental reports exist on small animal models. We sought to develop an in vivo rat model of AF using a transvenous catheter and to evaluate the model's underlying characteristics.
  
  
  RESULTS
  Echocardiogram, surface electrocardiogram (ECG), and atrial effective refractory period (AERP) were recorded at baseline in young (3 months) and middle-aged (9 months) Wistar rats. AF inducibility and duration were measured through transvenous electrode catheter in young (n = 11) and middle-aged rats (n = 11) and middle-aged rats treated with either pilsicainide (1 mg/kg iv, n = 7) or amiodarone (10 mg/kg iv, n = 9). Degrees of interstitial fibrosis and cellular hypertrophy in the atria were assessed histologically. The P-wave duration and AERP were significantly longer and echocardiographic left atrial dimension significantly larger in middle-aged versus young rats. AF was inducible in >90% of all procedures in both untreated rat groups, whereas AF inducibility was reduced by the antiarrhythmic drugs. The AF duration was significantly longer in middle-aged than in young rats and was significantly shortened by treatment with either pilsicainide or amiodarone. Histologic analysis revealed significant increases in atrial interstitial fibrosis and cellular diameter in middle-aged versus young rats.
  
  
  CONCLUSIONS
  Transvenous catheter-based AF is significantly longer in middle-aged than in young rats and is markedly reduced by treatment with antiarrhythmic drugs. This rat model of AF is simple, reproducible, and reliable for examining pharmacologic effects on AF and studying the process of atrial remodeling.
authors.affiliation: Cardiovascular Division, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Dongzhu
authors.initials: D
authors.lastname: Xu
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Murakoshi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tada
authors.forename: Miyako
authors.initials: M
authors.lastname: Igarashi
authors.forename: Yukio
authors.initials: Y
authors.lastname: Sekiguchi
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
mesh_terms: D000375:Aging; D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000662:veterinary*; D006328:Cardiac Catheterization / Q000662:veterinary*; D002304:Cardiac Pacing, Artificial / Q000662:veterinary*; D004195:Disease Models, Animal; D006801:Humans; D008297:Male; D051381:Rats; D017208:Rats, Wistar