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.