Echocardiographic evidence of left atrial mechanical dysfunction after conversion of atrial fibrillation to sinus rhythm in 5 horses.
Authors: Schwarzwald Colin C, Schober Karsten E, Bonagura John D
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Atrial fibrillation (AF) causes structural and functional changes to the heart, but whether horses experience the same post-conversion complications documented in other species has remained unclear until now. Schwarzwald and colleagues used transthoracic echocardiography—specifically two-dimensional imaging, transmitral Doppler flow analysis, and tissue Doppler imaging—to assess left atrial mechanical function in five Standardbred horses immediately after pharmacological or electrical conversion from AF to normal sinus rhythm, comparing their findings against six healthy controls. The researchers identified significant deterioration in left atrial contractile and reservoir function within 24 hours of successful cardioversion, though these markers of dysfunction had substantially recovered by 72 hours post-conversion, albeit with variable recovery trajectories between individual animals. These findings suggest that AF-induced atrial remodelling does occur in horses, similar to other species, and represents a transient but measurable period of mechanical dysfunction that practitioners should be aware of when monitoring recently converted horses. For equine veterinarians and performance professionals, this work highlights that successful rhythm conversion does not immediately restore normal atrial function, and advocates the value of ultrasound assessment during the early post-conversion period to detect and monitor left atrial recovery.
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Practical Takeaways
- •Horses recovering from atrial fibrillation conversion may experience temporary left atrial dysfunction for 24-72 hours; echocardiographic monitoring can assess recovery trajectory
- •Both pharmacological (quinidine) and electrical cardioversion can be effective in horses, with similar post-conversion mechanical outcomes
- •Most horses show spontaneous improvement in atrial function within 72 hours of successful cardioversion, suggesting close monitoring rather than intervention may be appropriate during early recovery
Key Findings
- •Left atrial contractile and reservoir function significantly decreased 24 hours after cardioversion in 5 horses with AF converted to sinus rhythm
- •Echocardiographic dysfunction was no longer statistically significant by 72 hours post-conversion, though individual variation existed
- •Two-dimensional echocardiography, transmitral Doppler flow, and tissue Doppler imaging can detect LA mechanical dysfunction in horses after AF conversion
- •AF-induced atrial remodeling likely explains the transient mechanical dysfunction observed after cardioversion