A stallion in Belgium has undergone a successful cardiac ablation to correct a heart arrhythmia in the first operation of its kind in the world.
Ablation had never been used in a horse before, partially because adult horses do not fit in a CT or MRI. But specialists from the University of Ghent’s Equine Cardio team guided the whole procedure by cardiac ultrasound.
Three-dimensional recording of all electrical activity in the heart, a technique called ‘mapping’ was first needed to find the precise spot in the heart where the arrhythmia originated from.
Local destruction of the tissue by ablation (heating of tissue) subsequently restored the normal heart rhythm in the Norwegian showjumper.
Lead veterinarian professor Gunther van Loon said the technique opened broad perspectives for treatment of arrhythmias in horses or other large animals in future.
Cardiac arrhythmias in horses
A cardiac arrhythmia is an electrical problem that causes the heart to beat irregularly. Abnormalities of the cardiac rhythm occur frequently in horses. Some are innocent but most arrhythmias affect performance or might even be a risk for collapse or sudden death. Accurate diagnosis is therefore important.
Anti-arrhythmic drugs may be used to attempt to restore a normal rhythm. In the past the Equine Cardio team has used pacemaker implantation in horses for arrhythmias that cause the heart to beat to slowly.
In 2001, electroshock treatment was developed at Ghent University to treat arrhythmias by electroshock with a success rate of more than 95%. But successfully treated horses, may show recurrence and may need a second treatment. This was also the case for the Norwegian showjumper who was successfully treated several times by electroshock therapy but each time the arrhythmia recurred.
In human medicine, many patients experience recurrence of atrial arrhythmias. The reason is that specific ‘diseased’ groups of cells reinitiate the arrhythmia because they are electrically unstable. Ablation, a technique that inactivates these diseased cells by heating or cooling, can dramatically reduce the risk of recurrence. Advanced imaging techniques such as CT and MRI are needed to exactly localize the ablation catheters in the heart.
Ablation in horses
Previously, ablation had never been performed in horses, whose thorax is too large to fit into a CT or MRI. Therefore, the Equine Cardioteam guided the whole procedure of ablation by ultrasound. First, under general anaesthesia, a full 3D image of the atria with all electrical activation patterns was recorded by an advanced intracardiac ‘mapping’ technique. This examination allowed them to identify the group of diseased cells that created the arrhythmia in the horse.
Subsequently, an ablation catheter was guided to the right spot in the heart to destroy the diseased cells by ablation. Normal heart rhythm immediately resumed.
The horse made a full recovery from the four-hour operation and is scheduled to return to competition soon.
Buoyed by its success, the Equine Cardioteam at Ghent University will further develop the mapping and ablation technique.