Atrial fibrillation in performance horses: more common?

[Dusty85]

So after the news of Miner's frolic retirement due to an episode of AF,a recent similar episode in Sprinter sacre, and a few years back Denman (and doubtless others that I don't know of); is this something that is becoming more common or do you think we're maybe just picking it up sooner?
Are we putting too much cardiovascular strain on these types of horses that means they are more likely to develop it?

I'm sure this is something that is more common in the performance horse that are pushed to the physical extremes.
Has anyone had their horse have an episode of AF? Or other arrhythmia for that matter?

Just a little musing- I wondered what other people's opinions were?

Tea and toasted hot cross buns on offer

 

[ladyt25]

I think athletes, whether human or horse often develop AF due to the heart being pushed. I imagine the reason we hear more about it now is, as you've said, because we're better at picking up on it. I believe they just used to be referred to as 'murmurs' ( if you see any get cert where it's mentioned), and often it is just apparent at rest but would disappear once the horse was being worked/after work

 

[glenruby]

A fib would never have been referred to as a"murmur" as it bears no resemblance to one - it's an arrhythmia. It's been diagnosed and treated very regularly over the last 20 years or so - the only difference is that the owner/trainers of these horses have chosen to tell the media the cause of their poor performance.

ETA - no advanced equipment are needed to diagnose this - just a stethoscope with ECG follow up. Also it does not disappear with exercise. It can be associated with murmurs or concurrent disease.

 

[Dusty85]

Totally agree with you glenruby- it's not a murmur (that is a valve problem that causes an abnormal sound as the blood passes through) but does make me wonder how many of us that horses with slow AF, I mean how many of us listen to our horses hearts? Or feel their pulses?

 

[Ruth17]

Totally agree with you glenruby- it's not a murmur (that is a valve problem that causes an abnormal sound as the blood passes through) but does make me wonder how many of us that horses with slow AF, I mean how many of us listen to our horses hearts? Or feel their pulses?

No such thing as slow AF unless you're on medication such as a beta blocker or digoxin.

AF is an arrhythmia which can happen for many reasons but usually in humans it's stress or MI related. Don't really think it's linked to being an athlete, probably less likely in athletes as they are more likely to have better cardiovascular health

 

[fburton]

Athletes can have physiological cardiac hypertrophy, and enlarged atria tend to facilitate AF. The naturally large size of horses' atrial may predispose them to atrial arrhythmias compared to e.g. human, even without hypertrophy.

 

[Dusty85]

No such thing as slow AF unless you're on medication such as a beta blocker or digoxin.

Sorry but this isn't true. Many people can have slow AF (permanent or paroxysmal) but only actually notice it when they flip into fast AF. Or it's just picked up incidentally.

Athletes are more likely to have HOCM though, which predisposes to arrhythmias, although not necessarily AF. It usually arises when there is either structural damage (such as post MI) or atrial dilation.

 

[norfolk_grump]

Just for the record. You can have AF with a slow ventricular rate without medication (you can also have AF with a regular ventricular rate).

 

[glenruby]

It is more commonly noticed in high performance horses as at low exercise intensities the clinical signs (mainly exercise intolerance and fatigue) are often not apparent. In the case of hacks and leisure horses, as Dusty said it is usually not picked up by their owners however this is where the importance of at least a cursory cardiac auscultation at vaccination is most apparent as I have picked up two at vaccination. Fburton is correct in that the large side of the horses heart predisposes them to A fib and this is definitely more of an issue in the more athletic horses. Equine cardiology actually differs quite a bit from human cardiology.

 

[norfolk_grump]

"Equine cardiology actually differs Quite a bit from human cardiology" Thankfully!
What are the major differences in the physiology?

 

[Ruth17]

Sorry but this isn't true. Many people can have slow AF (permanent or paroxysmal) but only actually notice it when they flip into fast AF. Or it's just picked up incidentally.

Athletes are more likely to have HOCM though, which predisposes to arrhythmias, although not necessarily AF. It usually arises when there is either structural damage (such as post MI) or atrial dilation.

HOCM is a genetic condition not related to being an athlete. You are talking about HCM.

 

[fburton]

Equine cardiology actually differs quite a bit from human cardiology.

And yet, amazingly, if you were to look at a heart cell (ventricular myocyte) from a horse and from a human, you'd be pushed to tell the difference.

 

[Orangehorse]

There is one vet book where it says that horse owners who are also doctors can't resist listening to their horse's heart through their stethoscope, and then get worried, and have to be reassured by the vet that horse and human hearts are different.

All the techinical stuff is rather above my head - interesting nevertheless - but I do notice that my vet always listens to the heart and lungs before vacinations which is always slightly nerve-wracking.

 

[Dusty85]

HOCM is a genetic condition not related to being an athlete. You are talking about HCM.

HCM is the genetic one; autosomal dominant. HOCM is idiopathic and just describes HCM but where the blood outflow is obstructed. (It is usually the latter that causes sudden death)

Haha orange horse- I've listened to my own, my dog's and my horses heart!

 

[norfolk_grump]

HCM and HOCM are the same genetic disorder but have slightly different phenotypes (asymmetrical hypertrophy v asymmetrical hypertrophy with obstruction). The gene is autosomal dominant with partial penetrance.
Do horses have a marked sinus arrhythmia? My dogs do and I did have a little panic when I felt their apical beats!