Abstract 743: Atrial Fibrosis in Dog Model of Atrial Fibrillation with Intact AVN and Heart Failure, Ablated AVN and Normal LV vs. Normal hearts. A case for Early Rhythm Control
Introduction: This study examines the electro-pathological effects of 3 month of atrial fibrillation (AF) in dog model of AF with and without concomitant heart failure (HF) compared with normal dogs.
Methods: Three groups of dogs (35±2 kg) were studied. In Group 1 (n=7), the atria were paced at 650 bpm to induce chronic AF as well as heart failure due to rapid ventricular response (160 –210 b/m). In Group 2 (n=6), the AVN was ablated and AF induced by pacing the atria at 650 b/m while the ventricle was paced at 80 b/m. Group 3 (n=9) consisted of normal sham dogs. The dogs in groups 1 and 2 were converted to NSR by DCCV and monitored in NSR for 3 months followed by retesting of AF susceptibility. Tissue fibrosis was assessed at 18 sites in the RA, LA and LV by trichrome-staining and quantitative immunohistochemistry (QIHC).
Results: AF was induced within 12±4 days and 30±13 days respectively in groups 1 and 2 (p<0.01). After 3 months of persistent AF, LVEF was 30.4±10.1% and 55±5% in groups 1 and 2, respectively (p<0.01 Group 1 vs. 2). AF induction was reassessed after 3 months of NSR. AF was induced in 4±2 and 2.6±2 days in groups 1 and 2 respectively (p<NS). In each of the 3 groups, there were no regional differences in the amount of fibrosis within atria and no differences in the abundance of fibrosis in LA vs. RA. Atrial fibrosis was greater in Groups 1 and 2 versus Group 3. Ventricular fibrosis was significantly increased in the in intact AVN and HF group 1 vs. group 2 and 3 (Table⇓).
Conclusions: 1. Three months of AF in combination with rapid ventricular response leading to HF results in a significant increase in atrial and ventricular fibrosis vs. AF alone with NL LVEF. 2. AF without HF results in atrial fibrosis suggesting that AF alone causes atrial fibrosis. 3. Rapid ventricular response from AF should be controlled to prevent HF. 4. If rhythm control is sought, conversion to NSR should be done as early as possible to avoid atrial fibrosis and the increase susceptibility to AF.