A series of high-profile horses suffering from a heart irregularity known as atrial fibrillation (AF) has brought the condition into the public eye.
It has emerged that William Fox-Pitt’s Parklane Hawk suffered an AF during the cross-country at Badminton Horse Trials (10 May). The horse fell 3 fences from home after what had been a fabulous round.
AF is a disorder of the heart which causes its regular rhythm to become interrupted and go out of sync. It happens when the electrical impulses that control the heart rate become chaotic.
The Bournemouth Echo reported Parklane Hawk’s rhythm corrected itself by the following morning, but he is 1 of several well-known horses to suffer from the condition in the past 6 months.
Tina Cook decided to retire Miners Frolic after he suffered from the condition while out on a hack which did not swiftly correct itself. Top chaser Sprinter Sacre has not raced since being pulled up at Kempton in December and subsequently being diagnosed with the same condition.
William did not want to comment on when Parklane Hawk will return to work or competition.
Andy Bathe, former vet to the British eventing team, told H&H that other horses at Badminton had also suffered from irregular heartbeats.
“Horses undertaking strenuous effort and horses with big hearts are predisposed to it,” said cardiology expert Dr Lesley Young.
“A difficult and arduous course will increase the risk because the harder the horse is having to work, the greater the effort and the more metabolic disturbances are taking place that could impact the heart.”
The condition is much more noticeable in a horse who is working at its athletic limit.
“If it happens acutely on the course the horses tend to pull up like they have run out of gas. They stop as if they have been shot,” Dr Young added.
“But there can be a lot of variation. With horses working at a lower level, it often won’t be picked up on until a routine check.”
The condition does not just affect event and racehorses. It is also often seen in hunters, draught horses and polo ponies.
A group of combined US and European specialist equine vets have recently reviewed recommendations for managing equine athletes with cardiovascular abnormalities and produced advice on how to manage cases.
Treatment options
In some cases, horses’ heart rates will naturally readjust themselves within 48hr. Dr Young estimates that around two-thirds of horses she has seen whose hearts correct themselves within that time period do not experience a recurrence of the problem.
For horses who do not adjust themselves there are 2 treatment options — medical treatment, usually quinidine, or electrical cardioversion (see below).
Horses who undergo either treatment successfully can return to normal work — but there is still the risk that it might happen again.
“There are plenty of high-profile horses who have had atrial fibrillation and then carry on,” Dr Young said.
Olympic dressage silver medallist Jerich Parcival underwent electrical cardioversion for atrial fibrillation last summer. His rider Adelinde Cornelissen announced earlier this month (7 May) that he is now being aimed for the World Equestrian Games in August.
Why now?
Vets believe that the recent spate of top horses suffering from AF is nothing more than a coincidence.
“I don’t think there is any particular reason,” Andy Bathe said. “It is probably just a cluster of cases that happen to have affected horses who are in the public eye.”
“I think the equestrian public are generally more aware then they used to be,” Dr Young added. “But if anything we used to see more cases in eventing when there was still the long-format and horses were tested in the 10-minute box.”
Treatment options
Quinidine
This is the most commonly used drug treatment to convert horses with persistent AF back into normal rhythm. It has to be given in multiple doses by stomach tube. The treatment can have side effects including diarrhoea, depression and colic, but it is reported to be successful in more than 80% of cases.
Electrical cardioversion
This procedure has recently been introduced as an alternative, especially for horses where quinidine is either ineffective or not well tolerated. The procedure requires a general anaesthetic and specialised equipment to enable an electrical shock to be passed through the heart to restore the rhythm.
This article was first published in the 22 May issue of Horse & Hound magazine