Résumé
This study describes the prevalence of cardiac dysrhythmias occurring over a single 24 h period in ponies and compares the heart rate and frequency of dysrhythmias in two groups of ponies of different ages. Electrocardiograms were recorded using a Holter monitoring system from twenty four ponies aged less than 15-year-old [n = 14] and greater than 15-year-old [n = 10]. Subsequent analyses of cardiac rhythm revealed that only 3/24 ponies maintained a regular rhythm throughout the recording period. In the remaining 21 ponies, 6 different types of dysrhythmias were detected, the majority of which were vagally mediated; sinus arrhythmias [n = 12], sinoatrial block [n= 6] and second degree atrioventricular block [n = 10]. Premature beats of both atrial [n = 3] and ventricular [n =1] origin were observed only in the older group. There were no significant differences between the 2 groups with respect to mean 24-h heart rates or the prevalence of cardiac dysrhythmias