Effects of Continuous Training on the Induction of Atrial Fibrillation in a Rabbit Model

  Objective  This study was aimed to assess mechanisms underlying continuous training induced atrial fibrillation (AF) in an animal model.

  Methods  Healthy New Zealand rabbits were divided into three groups (n=12 each): control group (C), moderate intensity group (M), and high intensity group (H). The intensity of continuous training was adjusted according to the treadmill speed. After 12 weeks of training, with a Langendorff perfusion system, AF was induced by S1S2 stimulation and the incidence was recorded. Changes in atrial kir2.1, kir2.2, type Ⅰ and Ⅲ collagen protein mRNA expressions were assessed by quantitative real-time PCR. Masson staining was used to assess the extracellular collagen volume fraction (CVF) .

  Results  After 12 weeks, comparing with group C, groups M and H had greater (P<0.05): CVF, incidence of AF (P<0.05, also between Groups H and M), and atrial inward rectifier potassium current/channel (IK₁) . In Group H, kir2.1, kir2.2, type Ⅰ and Ⅲ collagen protein mRNA expressions in the left atrium were increased (P<0.05, compared with Groups C and M).

  Conclusion   Long-term and high-intensity treadmill running could increase AF incidence in rabbits.