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== Introduction ==

== Introduction ==

Atrial fibrillation is the commenest pathological dysrhythmia. It is common in horses and cattle, but rare in cats and dogs.

Atrial fibrillation is the commonest pathological dysrhythmia. It is common in horses and cattle, but rare in cats and dogs.

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== Clinical Signs ==

== Clinical Signs ==

This may be an incidental finding on clinical examination, especially if the horse is not used for highly atheletic activities. If the horse is raced, hunted or an eventer etc, then signs may occur during exercise and include exercise intolerance, reluctance to exercise or a poor performance during exercise. It can be associated with exercise induced pulomonary haemorrhage, so this can be a clinical sign of the condition.

This may be an incidental finding on clinical examination, especially if the horse is not used for highly athletic activities. If the horse is raced, hunted or an eventer etc, then signs may occur during exercise and include exercise intolerance, reluctance to exercise or a poor performance during exercise. It can be associated with [[Exercise Induced Pulmonary Haemorrhage|exercise induced pulmonary haemorrhage]], so this can be a clinical sign of the condition.

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== Diagnosis ==

== Diagnosis ==

A full history and clinical examination may provide a presumptive diagnosis for this condition. Findings on clinical examination will include an irregularly irregular heart rhythm on auscultation with no fourth heart sound. The heart will sound 'chaotic'. There may also be a varibale pulse quality and a variable intensity of heart sounds.

A full history and clinical examination may provide a presumptive diagnosis for this condition. Findings on clinical examination will include an irregularly irregular heart rhythm on auscultation with no fourth heart sound. The heart will sound 'chaotic'. There may also be a variable pulse quality and a variable intensity of heart sounds.

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An electrocargiogram (ECG) can be performed and will provide a definitve diagnosis. It will show a lack of P waves and instead 'F waves' (atrial fibrillation). There will be small f waves (atrial flutter). There will be an irregular R- R interval due to random depolarisation of the AV node. QRST complexes will all be normal and alike in appearance.

An electrocargiogram (ECG) can be performed and will provide a definitive diagnosis. It will show a lack of P waves and instead 'F waves' (atrial fibrillation). There will be small f waves (atrial flutter) and an irregular R-R interval due to random depolarisation of the AV node. QRST complexes will all be normal and alike in appearance.

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== Treatment and Control ==

== Treatment and Control ==

It is vital that all underlying causes of the condition are diagnosed and treated as this will treat the Atrial Fibrillation. In horses where the condition is often found in normal animals without concurrent heart disease, treatment is with the drug quinidine sulphate. This drug acts by prolonging the effective refractory period. The horse should be given quinidine sulphate concurrently with digoxin, which will have been started two days prior to commencing quinidine sulphate. Quinidine sulphate should be given every two hours by stomach tube until conversion to sinus rhythm, or until six doses have been given. There are some severe side effects which can occur with this treatment and they include ventricular tachycardia, colic, diarrhoea and hypotension.

It is vital that all underlying causes of the condition are diagnosed and treated as this will treat the atrial fibrillation. In horses where the condition is often found in normal animals without concurrent heart disease, treatment is with the drug quinidine sulphate. This drug acts by prolonging the effective refractory period. The horse should be given quinidine sulphate concurrently with digoxin, which will have been started two days prior to commencing quinidine sulphate. Quinidine sulphate should be given every two hours by stomach tube until conversion to sinus rhythm, or until six doses have been given. There are some severe side effects which can occur with this treatment and they include ventricular tachycardia, [[:Category:Colic in Horses|colic]], diarrhoea and hypotension.

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Cattle with the condition  should also be treated with the same protocol.  

Cattle with the condition  should also be treated with the same protocol.  

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[[Category:Altered_Supraventricular_Impulse_Formations]][[Category:To_Do_-_Review]]

[[Category:Altered_Supraventricular_Impulse_Formations]]

[[Category:Cardiovascular Diseases - Cattle]][[Category:Cardiovascular Diseases - Horse]]

[[Category:Expert_Review]]