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Background:Models of naturally occurring atrial fibrillation (AF) are currently notavailable. Horses, like humans, may develop AF spontaneously2.However, little is known about AF patterns in horses and theirrelationship to heart dimensions. Large atrial dimensions might offer agood substrate for AF perpetuation.Objective:To understand if and how cardiac dimensions participate to AFperpetuation using the well-characterized goat model of AF as areference.
Does size matter? Characterization of a horse model of chronic atrial fibrillationGiulia Gatta1*, Merle F. Fenner4*, Stefan Sattler2, Ulrich Schotten1, Thomas Jespersen3, Sander Verheule1, Arne van Hunnik1, Rikke Buhl4
1Department of Physiology, Maastricht University, The Netherlands, 2Department of Cardiology, Heart Centre, Copenhagen; University Hospital Rigshospitalet Copenhagen Denmark, 3Department of Biomedical Sciences, University of Copenhagen, 4Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark; *contributed equally
Methods:
§ Equine ECG parameters are scaled to body size, but local atrial electrograms are comparable after 4 weeks of AF
§ The relative AF complexity is higher in horses due to atrial dimensions
§ AF stabilization is facilitated by electrical remodeling
§ At constant rate of pacing ERP and CV are comparable§ Absolute wavelength is longer in horses than in goat
§ Conclusion: size difference may serve as an adequate substrate for AF stabilization
• Eleven horses and nine goats in persistent AF (4w) were included.• Conduction velocity (CV) and ERP were measured with S1-S1 and S1-S2 protocols.• Wavelength (WL) was defined as ERP x CV.• Conduction patterns were recorded with high-density arrays (249 unipoles) on both atria
simultaneously during an open-chest experiment.• Fibrillatory waves were reconstructed based on activation times using a probabilistic approach. This
allowed AFCL quantification and AF patterns reconstruction.• Pathlength (PL) was defined as AFCL x CV.• Statistics: if not stated otherwise, student T-test. p < 0.05 was considered as statistically significant.
Giulia [email protected]://afib.ku.dk/early-stage-researchers/giulia-gatta/
This project has received funding from the European Union'sHorizon 2020 research and innovation programme under theMarie Skłodowska-Curie grant agreement No. 675351.
Horse
Goat
Horse Goat
References:1. Wijffels, M. et al., (1995). Circ., 92(7), 1954-1968.
2. Reef, V. et al., (2014). J. of Vet Int Med, 28(3), 749-761.
Sustained = AF episodes > 24h
SR
AF
1 sec
Horse GoatN 11 9
Body weight 469.56 ± 68.18 55.750 ± 3.31
Heart weight (kg) 3.62 ± 0.34 0.35 ± 0.6
Atrial circumference (cm) 58 ± 4.6 25 ± 2.7
Ventricular length (cm) 22 ± 2.2 11 ± 1.5
Heart Rate (bpm) 33 ± 5
PQ (ms) 298 ± 44 235 ± 162
RR (ms) 1765± 60
QT end (ms) 609 ± 47 199 ± 84
QRS width (ms) 166 ± 137 30.06 ± 7.32
AF stabilization occurs after few days of pacing. Shortening of AFCL indicated electrical remodeling ofthe atrial tissue. The ECG shows prolonged repolarization and slower intrinsic SR in the horse than ingoat. However, during regular rhythm at atrial level we find small differences between the models. Thesame is true for epicardial electrograms of persistent AF and for the degree of AF complexity within themapped area. However, the normalization for the atrial circumference reveals that many moreconduction patterns are theoretically possible. Thus, the heart size may play a role in AF stabilization:1) The relative higher number of waves is indicative of highly dynamic and complex AF patterns2) Long relative pathlength & short ERP are the ideal setup for the establishment of reentrant circuits.
Horse
Goat
Isochrone = 5ms step
ECG parameters and dimensions
2-way ANOVA, multiple comparisons (Bonferroni)
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Normalization for the atrial circumference shows significantdifference between models
§ Horses show similar AF properties to goats
