Key result
Chronic atrial fibrillation in a canine model significantly decreased left atrial mean bipolar amplitude from 5.96 mV at baseline to 3.23 mV (P<.01), alongside increased dominant frequency and fibrosis.
Why the study?
The extent of structural and electrophysiological remodeling with long-term AF is not well characterized.
Does long-term chronic AF induced by neurostimulation alter atrial electrophysiological and structural substrate in a canine model?
Does long-term chronic AF induced by neurostimulation alter atrial electrophysiological and structural substrate in a canine model?
In a canine model, chronic AF leads to significant decreases in intracardiac bipolar amplitudes and increases in dominant frequency and tissue fibrosis, though amplitudes remain higher than traditional cut-offs for diseased tissue.
May caution voltage-based scar assessment in chronic AF; leaves open translation to human electroanatomic mapping.
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. 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.
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Yamashita et al. (2019) studied Atrial fibrillation (n=9). Neurostimulator implantation (AF induction) vs. Baseline / No implantation was evaluated on Mean bipolar amplitude in the left atrium (p=<.01). Chronic atrial fibrillation in a canine model significantly decreased left atrial mean bipolar amplitude from 5.96 mV at baseline to 3.23 mV (P<.01), alongside increased dominant frequency and fibrosis.
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