Causes of poor performance of horses during training, racing, or showing: 348 cases (1992–1996)

Abstract

Objective—To determine results for horses undergoing a high-speed treadmill examination, including videoendoscopy of the pharynx and larynx before and during exercise, echocardiography before and after exercise, and electrocardiography before, during, and after exercise, because of poor performance. Design—Retrospective study. Animals—348 horses. Results—A definitive diagnosis was obtained for 256 (73.5%) horses. One hundred forty-eight horses had dynamic obstruction of the airway during exercise, 33 had clinically important cardiac arrhythmias alone, 22 had a combination of dynamic airway obstruction and clinically important cardiac arrhythmias, 19 had poor cardiac fractional shortening immediately after exercise, 10 had exertional rhabdomyolyis, 15 had clinically apparent lameness, and 9 had other disorders. Thirtynine of the horses with dynamic obstruction of the airway during exercise had multiple airway abnormalities. Fifty-three horses also had subclinical myopathy. Conclusion and Clinical Relevance—Results suggest that a complete evaluation, including a highspeed treadmill examination, should be conducted in horses with poor performance, regardless or whether horses do or do not have a history of abnormal respiratory noises and particularly if the horses have grade- II or -III left laryngeal hemiplegia. (J Am Vet Med Assoc 2000;216:554–558)