Update on Exercise-Induced Pulmonary Hemorrhage

Key points

How common is exercise-induced pulmonary hemorrhage?

EIPH has been identified in virtually all breeds of horses used for flat racing, harness racing, hurdle and steeplechase racing, polo, western performance disciplines, eventing, show jumping, and dressage. The prevalence of EIPH varies according to the type of exercise performed, the population of horses examined, the criteria used to define EIPH (epistaxis vs tracheobronchoscopic severity grade vs cytologic evidence of EIPH), and the frequency of examinations. Using tracheobronchoscopy

How does exercise-induced pulmonary hemorrhage occur?

Currently, the accepted pathophysiologic mechanism of EIPH is stress failure of the pulmonary capillaries caused by excessive transmural pressure created by very high intracapillary pressure (predominantly caused by high blood pressure) and low intra-alveolar pressure (generated by negative intrapleural pressures associated with inspiration) produced during exercise.¹⁰

Strenuous exercise in horses is associated with marked increases in pulmonary vascular pressures. Mean pulmonary arterial

What are the risk factors for exercise-induced pulmonary hemorrhage?

Risk factors for EIPH or epistaxis have been investigated in multiple studies of Thoroughbred and Standardbred racehorses in the United Kingdom, Australia, South Africa, Brazil, Japan, Hong Kong, and the United States. Although some risk factors seem common to EIPH and epistaxis, the risk factors for either condition are not identical. As a general rule, the more intense the exercise or higher the speed attained, the greater the proportion of horses detected with EIPH or epistaxis. The

What is the impact of exercise-induced pulmonary hemorrhage on performance?

Historically, there were conflicting results of the impact of EIPH on performance. Associations were detected with inferior or superior racing performance, or no association was detected at all.1, 2, 36, 37 These conflicting results were generated from studies that used different statistical methods, populations of horses, study methodologies, and diagnostic criterion and the lack of methodologically robust, large-scale studies evaluating the association between EIPH and performance. Over the

What treatments are effective for exercise-induced pulmonary hemorrhage?

A wide variety of medications have been used to treat EIPH. Most medications address a putative pathophysiologic mechanism and/or an etiologic factor that has been implicated in the development of the disease during the last 40 years. The aims of treatment include a reduction in the severity of bleeding and prevention of any potential adverse pulmonary sequelae (eg, pulmonary inflammation, infection, or fibrosis). Despite substantive efforts to identify alternative, effective treatments for

Is exercise-induced pulmonary hemorrhage a progressive disease?

There is evidence that EIPH is a progressive disease. Horses without EIPH that have not raced or exercised strenuously do not show the typical gross postmortem and histologic lesions characteristic of horses with moderate to severe EIPH. Typical histopathologic lesions identified in horses with moderate to severe EIPH include bronchiolitis, bronchial angiogenesis, veno-occlusive remodeling, and fibrosis.⁶⁴ EIPH is often identified on postmortem evaluations of horses that die suddenly during

Summary

EIPH is a disease that affects horses performing high-intensity exercise. The proximate cause of EIPH is pulmonary capillary stress failure. The pathophysiologic basis of the disease involves very high exercising pulmonary capillary pressures and very low pleural pressures created during exercise. An early and important pathologic lesion is veno-occlusive remodeling; however, whether this finding is cause or consequence of EIPH is not yet known. Moderate to severe EIPH is associated with