Equine Exercise-Induced Pulmonary Hemorrhage – NAVLE Study Guide

Overview and Clinical Importance

Exercise-induced pulmonary hemorrhage (EIPH) is defined as the presence of blood in the airways of horses following strenuous exercise. EIPH is recognized as one of the most common conditions affecting performance horses and is considered a disease by the American College of Veterinary Internal Medicine (ACVIM). The condition occurs in virtually all horses undergoing high-intensity exercise, with prevalence rates of 45-75% detected by endoscopy and greater than 90% when bronchoalveolar lavage (BAL) cytology is used for diagnosis.

EIPH has been documented in equine athletes for over 300 years. The famous racehorse Bleeding Childers (born 1716), great grand-sire of the legendary Eclipse, was named for his tendency to exhibit epistaxis after racing. Despite our long awareness of this condition, the exact pathophysiology remains incompletely understood, and optimal treatment strategies continue to evolve.

Pathophysiology

Pulmonary Capillary Stress Failure

The fundamental cause of EIPH is pulmonary capillary stress failure. During maximal exercise, horses experience extraordinary cardiovascular demands that exceed the structural capacity of their pulmonary vasculature.