ridecamp@endurance.net: Re: Missing Heart Beats

Re: Missing Heart Beats

C.M.Newell (reshan@deyr.ultranet.com)
Wed, 30 Apr 1997 12:43:35 -0400

At 09:59 AM 4/30/97 MDT, you wrote:
>Sue Cunningham wrote:
>>How common is it for endurance horses to miss heart beats and why do
>>they do it?
>>Is there some advantage to missing beats rather than just having a
>>slower heart beat?
>Missing heart beats is bad. All animals should have a steady rhythm
>at all times. A horse that is in good condition will have a slower
>and "bigger" heart beat. The heart will pump more blood per beat
>that a horse that is in not so good condition.

I disagree. Second degree heart block is quite common in horses,
particularly healthy and fit horses. Dropped beats are not at all unusual.
They are due to vagal tone, and are usually easily abolished by startling
the horse , or by jogging it for a short distance.

In addition, to quote John Bonagura, from "Current Therapy in
Equine Medicine 4":

"Arterial blood pressure can be regulated durin inappropriate
periods of sinus tachycardia by blocking impulses in the AV node
even as the
sinus rate increases. Examples include a horse that has suddenly
stopped submaximal exercise...must be appreciated as variations of

Sounds like a distance horse at a vet check, no?

--CMNewell, DVM

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