Thoracic aortic rupture and aortopulmonary fistulation in the Friesian horse: histomorphologic characterization.
Authors: Ploeg M, Saey V, Delesalle C, Gröne A, Ducatelle R, de Bruijn M, Back W, van Weeren P R, van Loon G, Chiers K
Journal: Veterinary pathology
Summary
# Thoracic Aortic Rupture in Friesian Horses: A Connective Tissue Disorder Aortic rupture represents a catastrophic but poorly characterised condition in horses, with particular prevalence in the Friesian breed despite its rarity in the general equine population. Researchers examined postmortem aortic tissue from 20 affected Friesian horses (aged 1–10 years) using histology and immunohistochemistry, stratifying findings into acute (20%), subacute (40%), and chronic (40%) presentations based on pathological features. All cases exhibited consistent hallmarks including mucoid accumulation, elastic laminae fragmentation, medial smooth muscle hypertrophy, and medial necrosis—progressing from mild patchy involvement in acute ruptures to severe midzonal necrosis in chronic lesions—alongside inflammation patterns that shifted from predominantly neutrophilic infiltration early on to hemosiderophages in established cases. Notably, subacute and chronic specimens demonstrated medial fibrosis with morphologically abnormal collagen deposition, suggesting an underlying connective tissue disorder affecting elastin or collagen metabolism rather than secondary inflammation. For practitioners managing Friesian horses, these findings highlight a heritable structural vulnerability; whilst the current research cannot predict rupture risk in living animals, understanding the progressive nature of aortic degeneration underscores the importance of careful cardiovascular assessment during routine examinations and warrants further investigation into genetic screening and potential nutritional or pharmacological interventions targeting connective tissue integrity.
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Practical Takeaways
- •Friesian horses have a breed-specific predisposition to aortic rupture that appears to be a connective tissue disorder; consider this in differential diagnosis for sudden death or cardiovascular collapse in this breed.
- •The progressive nature of aortic wall changes (acute to chronic stages) suggests some horses may survive initial rupture; necropsy findings can help determine lesion chronicity and inform breeding decisions.
- •Understanding that this is a primary elastic/collagen defect rather than secondary degeneration may guide future research into preventive screening or genetic testing for affected families.
Key Findings
- •20 Friesian horses with aortic rupture showed three pathologic stages: acute (20%), subacute (40%), and chronic (40%) based on histopathologic features.
- •All rupture sites displayed mucoid material accumulation, elastic laminae disorganization, smooth muscle hypertrophy, and medial necrosis ranging from mild (acute) to severe (chronic).
- •Inflammatory response evolved from neutrophilic infiltrates in acute cases to hemosiderophages in chronic cases, suggesting secondary inflammation to medial necrosis.
- •Histopathologic findings suggest an underlying connective tissue disorder affecting elastin or collagen in the aortic media specific to Friesian horses.