Atrial and ventricular electrical and contractile remodeling and reverse remodeling owing to short-term pacing-induced atrial fibrillation in horses.
Authors: De Clercq D, van Loon G, Tavernier R, Duchateau L, Deprez Piet
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Atrial Fibrillation-Induced Remodeling in Horses De Clercq and colleagues investigated how atrial fibrillation (AF) affects electrical and mechanical function in equine hearts, using surgically implanted pacemakers to induce and sustain AF in six horses whilst measuring atrial effective refractory period (AERP), AF cycle length, and atrial fractional shortening (a measure of contractile function) at baseline, after seven days of AF, and during recovery. Within hours of AF onset, significant electrical remodelling occurred: the AERP shortened dramatically from 261 to 171 ms at a standard pacing rate, the AF cycle length decreased from 239 to 194 ms, and atrial contractility deteriorated completely (fractional shortening dropped from 12% to 0%), with AF becoming persistent in two animals by day seven. Remarkably, upon restoration of sinus rhythm, all electrical and contractile parameters normalised within 48 hours, demonstrating substantial reverse remodelling capacity. These findings suggest that early intervention to convert AF back to normal rhythm offers the most favourable prognosis for recovery and return to work, as prolonged AF drives progressive electromechanical changes that, whilst reversible in the short term, may become more entrenched with longer duration—potentially explaining why prompt cardioversion improves clinical outcomes and recovery timescales in practice.
Read the full abstract on PubMed
Practical Takeaways
- •Early conversion of atrial fibrillation in horses is critical, as electrical and contractile remodeling begins within hours and can progress to persistent AF within 7 days
- •The rapid reversibility of AF-induced remodeling within 48 hours of successful conversion suggests early intervention can prevent permanent structural damage and preserve athletic function
- •Early return to training may be feasible after AF conversion given the demonstrated complete recovery of atrial and ventricular function within 2 days
Key Findings
- •Atrial electrical remodeling occurred within 4 hours of induced AF, with AERP shortening from 261±39 ms to 171±18 ms at PCL 1000 ms (P<0.0001)
- •Atrial contractile remodeling developed within 12 hours, with atrial fractional shortening decreasing from 12±3% to 0±2% (P<0.05)
- •AF cycle length decreased progressively from 239±39 ms to 194±7 ms over 7 days, with AF becoming persistent in 2 of 5 animals (P<0.0001)
- •Rapid reverse remodeling occurred within 48 hours of sinus rhythm restoration, with all electrical and contractile parameters returning to baseline values