Background: Atrial premature depolarizations (APDs) are a known risk factor for atrial tachycardia and atrial fibrillation, and are occasionally associated with reduced performance. A 12-lead electrocardiogram (ECG) and vectorcardiogram (VCG) might be helpful to localize the ectopic region but 3D electro-anatomical mapping (3D EAM) is the method of choice. Radiofrequency ablation might be used to inactivate ectopy.
Objectives: Describe electrocardiograms (ECGs), vectorcardiograms (VCGs), 3D EAM and treatment by ablation. Animals: Three horses with a high burden of APDs from the right atrial free wall (RAFW).
Methods: Records from 3 horses were reviewed.
Results: Horses presented between 7.000 and 15.000 APDs per 24-hour and 12-lead ECG and VCG suggested a RAFW origin. 3D EAM in two horses confirmed the RAFW origin. In the first horse, no ablation was performed as pacing (15 mA, 2 ms) of the ectopic region resulted in right phrenic nerve stimulation. The ectopic area was repetitively explored, which resulted in reduced ectopy, probably by repeated catheter pressure. The post-procedural ECG showed only 78 APDs per 24 hours. In the second horse, ablation was performed because the equine atrial wall thickness made phrenic nerve damage unlikely. After 18 applications, atrial ectopy disappeared. A 24-hour recording 6 weeks after the procedure showed only 7 APDs which was within normal limits.
Conclusions: The same RAFW region appeared the arrhythmogenic source of a high burden of APDS. The correct localization by VCG was confirmed by 3D EAM. Treatment by radiofrequency ablation was successful and did not result in side effects.
Learning Objectives:
appreciate the added value of 12-lead electrocardiography and vectorcardiography to identify an atrial ectopic rhythm
have insight into different techniques for 3D electro-anatomical cardiac mapping in horses
understand the possibilities and limitations of catheter radiofrequency ablation to treat cardiac arrhythmias
