Abstract
Simple SummaryAtrial fibrillation is the most common pathological cardiac arrhythmia affecting performance in horses. The sporadic form of atrial fibrillation, termed paroxysmal atrial fibrillation, spontaneously cardioverts to normal sinus rhythm usually within 7 days. The condition may go undetected, as episodes can occur intermittently at different frequencies and vary in duration from minutes to hours. However, paroxysmal atrial fibrillation may still result in poor performance, especially in racehorses, resulting in possible negative consequences for the horses and their owners. The epidemiology and pathophysiology of the disease are not well described. We investigate the current knowledge and present possible risk factors that may predispose horses to paroxysmal atrial fibrillation. Early diagnosis is crucial, which is why current and future diagnostic modalities are discussed.Atrial fibrillation (AF) is the most common arrhythmia in horses causing poor performance. As in humans, the condition can be intermittent in nature, known as paroxysmal atrial fibrillation (pAF). This review covers the literature relating to pAF in horses and includes references to the human literature to compare pathophysiology, clinical presentation, diagnostic tools and treatment. The arrhythmia is diagnosed by auscultation and electrocardiography (ECG), and clinical signs can vary from sudden loss of racing performance to reduced fitness or no signs at all. If left untreated, pAF may promote electrical, functional and structural remodeling of the myocardium, thus creating a substrate that is able to maintain the arrhythmia, which over time may progress into permanent AF. Long-term ECG monitoring is essential for diagnosing the condition and fully understanding the duration and frequency of pAF episodes. The potential to adapt human cardiac monitoring systems and computational ECG analysis is therefore of interest and may benefit future diagnostic tools in equine medicine.
Highlights
We focus on the early stages of Atrial fibrillation (AF) and the progression of paroxysmal AF (pAF) to persistent
Three cases of pAF were reported in neonate foals [63], but the triggering mechanisms are thought to be different compared to adult horses, and whether or not the incidence of equine pAF increases with age remains unknown
Horses at risk of developing pAF are racehorses performing at a maximal level of exertion and sudden loss of speed is the most common clinical sign
Summary
An unexpected and abrupt decrease in performance in horses without any previous clinical signs may be related to the sudden onset of cardiac arrhythmias [1]. Atrial fibrillation (AF) is the most common pathological arrhythmia in horses with poor performance. Numerous studies have investigated the mechanisms of AF in horses along with different treatment options and the effect on performance [9–11]. Less is known about pAF, likely due to its sporadic nature and lack of clinical signs in non-racing horses. Poor performance is a phrase commonly used to describe horses that do not meet the expectations their owners. In relation to pAF, poor performance has been used to describe even intermittent loss of physical capacity in racehorses, whereas for riding horses it describes a loss of energy and inability to perform the requested skills. More knowledge about pAF is needed, which is why we dissect here the current literature on pAF in horses and discuss possible future diagnostic modalities in equine cardiology
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