3.1.4 The use of the animal
The prevalence of cardiac disease differs little in animals used for different purposes. However, functional heart murmurs, and arrhythmias which are associated with high vagal tone such as second degree atrioventricular block (20 AVB), are more often noticed in racehorses. Some conditions which might go unnoticed in a pleasure horse may become clinically apparent in a perforanimal. For example, racehorses cannot perform normally with atrial fibrillation, but animals which are not required to perform rigorous exercise may have the condition without obvious clinical signs before it is discovered as an incidental finding.
The significance of cardiac disease may vary enormously depending on the use of the animal. A condition which renders an animal unsuitable for racing may not prevent it from performing normally as a hunter or, if it progresses further, from use as a hack. Rigid rules of thumb are inappropriate and the clinician should consider every case individually, in the light of the demands of the rider. Even the rider's ability and experience and the animal's temperament may need to be considered.