The atrial contraction only contributes to around 15% of the ventricular filling, so signs of atrial fibrillation are only seen during vigorous exercise. This may be an incidental finding on clinical examination, especially if the horse is not used for highly athletic activities. Ventricular response rate is variable, depending on the degree of physiological AV block.Ītrial fibrillation can occur in all species when there is atrial dilation secondary to other cardiac lesions. It may be seen as a precursor to atrial fibrillation. In animals with primary 'lone' AF, ventricular response rate may be normal or only mildly elevated due to parasympathetic influence on the AV node.Ītrial Flutter: is similar to atrial fibrillation, but has sudden onset and termination and is therefore a transient arrhythmia. In animals with underlying heart disease, the ventricular response rate is usually elevated due to sympathetic predominance.
It can occur in absence of structural heart disease (primary/lone AF), or secondary to underlying cardiac disease. As a result there is an irregular ventricular response. While the atria fail to contract some of the disorganised depolarisation waves are conducted through the AV node, reaching the ventricles. Atrial fibrillation is the commonest pathological dysrhythmia.Ītrial Fibrillation (AF): Occurs when many ectopic waves of depolarisation spread throughout the atria.
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