Lesion size index-guided radiofrequency catheter ablation using an impedance-based three-dimensional mapping system to treat sustained atrial tachycardia in a horse.
Authors: Buschmann Eva, Van Steenkiste Glenn, Vernemmen Ingrid, Demeyere Marie, Schauvliege Stijn, Decloedt Annelies, De Wilde Hans, van Loon Gunther
Journal: Equine veterinary journal
Summary
# Editorial Summary A 6-year-old Warmblood mare presenting with sustained atrial tachycardia at 191 beats per minute was successfully treated using impedance-based three-dimensional electro-anatomical mapping combined with radiofrequency catheter ablation, a sophisticated technique rarely documented in equine practice. The clinical team utilised vectorcardiography to localise the arrhythmia origin to the caudo-dorsal right atrium, then employed the EnSite™ Precision system to identify a clockwise macro-reentry circuit around a conduction block in the caudomedial right atrium—revealing the precise mechanism driving the arrhythmia. Under lesion size index guidance, ten radiofrequency applications (35 W, mean contact force 14 ± 3 g) were delivered to isolate the caudal vena cava myocardial sleeves, with normal sinus rhythm restored following the first ablation and entrance/exit block confirmed electrophysiologically. At nine-month follow-up, Holter monitoring showed no recurrence, demonstrating that this lesion size index-guided approach may offer superior outcomes by creating more effective substrate isolation and reducing arrhythmia recurrence in equine patients. For equine practitioners managing atrial tachycardias, this case highlights the value of advanced electrophysiological mapping and ablation techniques as definitive treatment options when pharmacological approaches are inadequate, though access to these technologies remains limited to specialist referral centres.
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Practical Takeaways
- •Radiofrequency catheter ablation guided by lesion size index and three-dimensional mapping can effectively treat sustained atrial tachycardia in horses with long-term success
- •This advanced electrophysiological technique may be considered for horses with drug-refractory arrhythmias when referral to centres with appropriate mapping technology is available
- •Careful identification and isolation of the arrhythmogenic substrate (such as caudal vena cava myocardial sleeves) appears crucial for preventing recurrence
Key Findings
- •Lesion size index-guided radiofrequency ablation successfully restored sinus rhythm in a 6-year-old mare with sustained atrial tachycardia (191/min) at the first energy application
- •Three-dimensional electro-anatomical mapping identified clockwise macro-reentry around a line of conduction block in the caudomedial right atrium
- •Isolation of caudal vena cava myocardial sleeves using 10 radiofrequency applications at 35 W and mean contact force of 14±3 g achieved entrance and exit block
- •No arrhythmia recurrence was observed on Holter monitoring at 5 days post-ablation and at 9-month follow-up