@phdthesis{01K8AQRAW32PM1DXB6SFHC44EP,
  abstract     = {{Supraventricular tachyarrhythmias are common in horses and pose a risk to both equine welfare and rider safety. Pharmacological or electrical cardioversion is currently used to treat atrial tachycardia and atrial fibrillation, but this approach leaves the arrhythmogenic tissue intact, making horses prone to recurrence. At present, no treatment options are available for frequently occurring premature atrial complexes or accessory pathways in horses.
Until now, the diagnosis of arrhythmias in horses has largely relied on surface electrocardiography, which can define the type of arrhythmia but does not provide insight into the mechanism or location of the arrhythmia. Invasive electrophysiological studies are needed for further investigation. In horses, advanced electrophysiological studies remained unexplored until recently due to limited imaging options. Recent developments in three-dimensional electro-anatomical mapping (3D EAM) in horses open new possibilities for more detailed electrophysiological studies. With the 3D EAM system, catheter positions in the heart can be visualised in real time without the need for additional imaging modalities, allowing precise identification of the arrhythmia’s origin. This paves the way for radiofrequency catheter ablation, in which targeted scar tissue is created to permanently eliminate the arrhythmia. Because horses have a large heart, thick myocardial walls, and high blood flow, ablation settings must be adapted to achieve durable and safe lesions.
The general aim of this PhD was to develop novel catheter-based diagnostic and therapeutic techniques for supraventricular tachyarrhythmias in horses. Mapping techniques, including multiple catheter recording and 3D EAM, were adapted for use in horses to unravel the underlying mechanism and origin of arrhythmias. In addition, to provide a permanent treatment for arrhythmias, the optimal ablation approach was determined. The final aim was to implement these techniques in the treatment of naturally-occurring arrhythmias in horses.
Multiple catheter recording in sinus rhythm and during right and left atrial pacing resulted in characteristic activation patterns. This can aid in identifying the origin of arrhythmia and opens up possibilities for electrophysiological studies in the standing horses. To optimise treatment by ablation, the effect of radiofrequency settings on lesion dimensions in equine myocardium using an in vitro model were described. To further optimise lesion formation, and thereby reducing recurrence risk, contact force-sensing catheters and the ablation index were used to isolate the caudal vena cava and pulmonary veins. The experience gained in these studies allowed to apply these techniques to diagnose and treat several types of naturally-occurring arrhythmias in clinical patients. Both impedance-based and magnetic-based 3D EAM systems were used and provided insights into the origin and mechanisms of arrhythmias. Typical atrial flutter in horses was identified as a macro-reentry circuit in the caudal right atrium. Caudal vena cava isolation, guided by the ablation index or lesion size index was effective to provide long-term freedom of atrial tachycardia in all horses. Furthermore, the mid right atrial free wall was identified as a predilection site of frequent premature atrial complexes in three horses, with a successful ablation performed in one horse. Electrocardiographic findings of accessory pathways in seven horses were described and were identified by 3D EAM in two horses. Although still challenging, ablation might provide a permanent solution for premature atrial complexes and accessory pathways. Challenges were mainly related to the thick equine myocardial wall and techniques to create deeper lesions should be investigated. Finally, the first experiences to reduce arrhythmogenic substrate in horses with recurrent, persistent atrial fibrillation by 3D EAM and radiofrequency catheter ablation were described, and indicated that recurrence was still observed. More research about the pathophysiology of equine atrial fibrillation is required to develop a targeted treatment. This PhD shows that mapping and ablation of supraventricular arrhythmias in horses is a highly promising technique to provide a permanent treatment.}},
  author       = {{Buschmann, Eva}},
  keywords     = {{Horse,Cardiology,Arrhythmias,Electrophysiology}},
  language     = {{eng}},
  pages        = {{295}},
  publisher    = {{Ghent University. Faculty of Veterinary Medicine.}},
  school       = {{Ghent University}},
  title        = {{Radiofrequency catheter ablation as a new treatment for supraventricular arrhythmias in horses}},
  year         = {{2025}},
}