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Equine Health Resource

Atrial Fibrillation

Atrial fibrillation is rapid and chaotic electrical activity and contraction of the atria of the heart. It can occur in a horse as a primary problem, or result from heart enlargement caused by other underlying heart disease.

The larger a horse’s atrium and heart get, the greater risk for this abnormal electrical activity. In congestive heart failure, the heart enlarges significantly as it becomes overloaded.

When atrial fibrillation exists without other heart disease, it is a performance limiting (but usually not life-threatening) condition, as it reduces the overall performance of the heart. Conversion to a normal rhythm is usually done with a drug called quinidine. However, this drug has some potentially life threatening side effects itself, and is only helpful in selected cases.

Prognosis & Relevant Factors

Fair, depends on the health of the heart otherwise, and the intended use of the horse. In the absence of other heart disease, the prognosis is good. There is about 20% recurrence.

The longer the condition exists, the harder it is to convert and recurrence is more likely.

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Author: Doug Thal DVM Dipl. ABVP


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