Changes in atrial electrophysiological and structural substrate and their relationship to histology in a long‐term chronic canine atrial fibrillation model

摘要

Abstract Background Atrial fibrillation (AF) is related to numerous electrophysiological changes; however, the extent of structural and electrophysiological remodeling with long‐term AF is not well characterized. Methods Dogs ( n ?=?6) were implanted with a neurostimulator in the right atrium (AF group). No implantation was done in the Control group ( n ?=?3). Electroanatomical mapping was done prior to and following more than 6 months of AF. Magnetic resonance imaging was also done to assess structural remodeling. Animals were euthanized and tissue samples were acquired for histological analysis. Results A significant increase was seen in the left atrial (LA) volume among all AF animals (22.25 ± 12.60 cm 3 vs 34.00 ± 12.23 cm 3 , P ?=?.01). Also, mean bipolar amplitude in the LA significantly decreased from 5.96 ± 2.17?mV at baseline to 3.23 ± 1.51?mV ( P ??.01) after chronic AF. Those significant changes occurred in each anterior, lateral, posterior, septal, and roof regions as well. Additionally, the dominant frequency (DF) in the LA increased from 7.02 ± 0.37?Hz to 10.12 ± 0.28?Hz at chronic AF ( P ??.01). Moreover, the percentage of fibrosis in chronic AF animals was significantly larger than that of control animals in each location ( P ??.01). Conclusions Canine chronic AF is accompanied by a significant decrease in intracardiac bipolar amplitudes. These decreased electrogram amplitude values are still higher than traditional cut‐off values used for diseased myocardial tissue. Despite these “normal” bipolar amplitudes, there is a significant increase in DF and tissue fibrosis.