Noninvasive determination of atrial fibrillation cycle length by atrial colour tissue Doppler imaging in horses.
Authors: Decloedt A, de Clercq D, van der Vekens N, Verheyen T, van Loon G
Journal: Equine veterinary journal
Summary
# Editorial Summary Atrial fibrillation cycle length (AFCL) reflects the degree of electrical remodelling occurring in the atria during AF, making it a valuable marker for understanding disease progression and evaluating treatment responses in affected horses. Decloedt and colleagues validated atrial colour tissue Doppler imaging (TDI) as a noninvasive method for measuring AFCL by comparing ultrasound-derived measurements against the gold-standard invasive electrogram recordings in 31 AF or flutter episodes across 29 horses undergoing transvenous electrical cardioversion. The invasive measurements revealed mean AFCL of 161±18 ms for AF cases, with two horses showing atrial flutter at substantially longer cycle lengths (244 and 324 ms), whilst tissue Doppler measurements demonstrated acceptable agreement with electrogram data (bias range −18 to +9 ms depending on anatomical region). Notable regional variation emerged, with the left atrial free wall measured from right parasternal and short-axis views consistently yielding shorter AFCL values than other atrial regions, suggesting heterogeneous electrical remodelling across the atrial tissue. This validation work offers clinicians and researchers a practical, repeatable ultrasound-based tool for non-invasively assessing electrical remodelling in horses with AF, enabling better characterisation of disease severity and potentially more informed decisions regarding antiarrhythmic therapy without requiring invasive cardiac catheterisation.
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Practical Takeaways
- •Veterinarians can now noninvasively assess atrial fibrillation severity and electrical remodelling using tissue Doppler ultrasound, eliminating need for invasive cardiac catheterization in many cases
- •Atrial fibrillation cycle length measurement via ultrasound allows better monitoring of drug efficacy and disease progression in horses undergoing treatment for AF
- •The wide limits of agreement (-18 to +9 ms) between methods suggest tissue Doppler can be useful for monitoring but should be used cautiously for precise absolute measurements in clinical decision-making
Key Findings
- •Noninvasive tissue Doppler imaging (AFCLTDI) can measure atrial fibrillation cycle length with mean bias of -18 to +9 ms compared to invasive electrogram measurement (AFCLEGM)
- •Mean AFCLEGM was 161 ± 18 ms in 29 AF episodes, with two horses showing atrial flutter with AFCLEGM of 244 and 324 ms
- •AFCLTDI measurements varied significantly by atrial wall region (P<0.001), being shorter in left atrial free wall regions than interatrial septum and right atrial wall
- •Tissue Doppler imaging identified spatial differences in electrical activity across equine atria and can assess atrial electrical remodelling without invasive procedures