Risk factors for atrial fibrillation and ventricular tachyarrhythmias in 3499 equids admitted at the liege university equine hospital between 1994 and 2011

Risk factors for atrial fibrillation (AF) and pathological ventricular tachyarrhythmias (VTA) have been suspected in equids, however little epidemiologic data exists. The aim of this study was to determine risk factors for AF and VTA in a large equine population. Case files of 3499 equids admitted to the internal medicine department of the Liege University Equine Teaching Hospital between 1994 and 2011were reviewed. Amongst them, 495 horses with a suspicion of a cardiac abnormality underwent ECG and echocardiography. After calculation of prevalence of AF and VTA, we tested whether breed (chi-square test) or gender, age, body weight (BW) and presence of other cardiac diseases (logistic regressions) were risk factors (significance set at p<0.05). In the studied population, prevalence of AF was high (2.3%), whereas prevalence of VTA was low (0.7%). Warmbloods and standardbreds were significantly overrepresented in AF cases. High BW was a risk factor for AF (OR=3.54; CI=1.67-7.49), whereas age was not. No effect of breed, age or BW was demonstrated for VTA. AF was observed significantly more frequently in horses presenting with moderate to severe mitral regurgitation (MR), tricuspid regurgitation, and pulmonary regurgitation, and VTA was significantly more frequent in horses with MR. Several previously suspected but not statistically demonstrated risk factors of AF were confirmed in this study and horses presenting valvular disease could be at increased risk of developing AF and VTA.