 This theory proposes how high pulmonary venous pressures may lead to the capillary rupture and the tissue changes observed in EIPH.Regional veno-occlusive remodeling, especially within the caudodorsal lung fields, contributes to the pathogenesis of EIPH, with the venous remodeling leading to regional vascular congestion and hemorrhage, hemosiderin accumulation, fibrosis, and bronchial angiogenesis.While all horses undertaking intense exercise experience some degree of EIPH, some horses consistently experience greater haemorrhage and other horses experience isolated episodes of increased EIPH.