The use of electrocardiographic recording with Holter monitoring during treadmill exercise to evaluate cardiac arrhythmias in racehorses

摘要

In equine medicine, particular attention is devoted to sports medicine and to the study of diseases affecting performance. In this regard the use of diagnostic tools, aimed at identifying any slightly abnormal condition, even those which may only appear during strenuous exercise, is desirable. Cardiac arrhythmias play an important role among cardio-vascular causes of poor performance, although this is still not completely understood. In athletic horses, bradyarrhythmias, such as sinoatrial block, second-degree atrioventricular block, wandering pacemaker and sinus bradycardia are frequently observed, although their clinical significance is usually negligible. On the other hand, other atrial rhythm disturbances (atrial fibrillation, atrial escape complexes, atrial tachycardia) and ventricular rhythm disturbances (ventricular escape complexes, ventricular tachycardia) may significantly affect athletic performance (Reef and Marr, 1993; Mitten, 1996). Moreover, the absence of rhythm disturbances at rest does not rule out their occurrence during maximal exercise and, conversely, the presence of cardiac arrhythmias at rest may not be related to poor performance. Therefore, it is essential to detect the occurrence and frequency of any rhythm disturbance during strenuous exercise. Holter monitoring, which is widely used in human medicine, has been recently proposed for equine patients (Baha, 1991; Raekallio, 1992; Reef and Marr, 1993; Scheffer et al., 1995; Bussadori et al., 1997).