Incidence of atrial fibrillation with mitral regurgitation in a Mix-breed athletic horse

Subject Areas : Veterinary Clinical Pathology

Hossein Khalesi ¹ ( Department of Clinical Sciences, Science and Research branch, Islamic Azad University, Tehran, Iran. )
mehdi sakha ² ( Department of Clinical Sciences, Science and Research branch, Islamic Azad University, Tehran, Iran. )
abbas veshkini ³ ( Department of Clinical Sciences, Science and Research branch, Islamic Azad University, Tehran, Iran. )
Ali rezakhani ⁴ ( Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. )

Received: 2021-10-18 Accepted : 2022-02-07 Published : 2022-01-21

Keywords: Arrhythmia, Atrial fibrillation, Mix-breed athletic horse, Mitral valve insufficiency,

Abstract :

Atrial fibrillation is one of the most important cardiac arrhythmias in athletic horses, which can be caused by cardiac valve insufficiency. This study reports the incidence of atrial fibrillation with mitral regurgitation in a Mix-breed athletic horse that showed cardiac murmur, poor performance and exercise intolerance. In a 5-year-old Mix-breed mare clinical examination, electrocardiography, hematological and biochemical serum tests, and echocardiography were performed to identify the causes of cardiac murmur and poor performance. In auscultation, an irregular-irregularity heart rhythm and the 4/6-degree holosystolic murmur with a maximum intensity point in the mitral valve region with trill, were heard. Then, the atrial fibrillation was recorded in base-apex lead electrocardiography. Increased levels of fibrinogen and white blood cells were detected in the hematological tests. Echocardiography showed flail leaflet of mitral valve, left ventricular dilatation, and moderate mitral regurgitation. The fractional shortening (FS) values were decreased that indicating a decrease in myocardial function. In mitral regurgitation, left atrium enlargement is part of the pathophysiological changes to compensate for the cardiac overload, but it will also be a sign of future heart disorders such as atrial fibrillation and even sudden death. Eventually, atrial enlargement with mitral regurgitation, atrial fibrillation and decreased fraction shortening can lead to poor performance and even a negative effect on horse's life expectancy.

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