Microvascular thrombosis associated with onset of acute laminitis in ponies.
Authors: Weiss, Geor, Johnston, Trent
Journal: American journal of veterinary research
Summary
# Editorial Summary: Microvascular Thrombosis in Acute Laminitis Weiss and colleagues (1994) investigated the long-standing hypothesis that laminitis originates from blood clot formation within the delicate vascular network of the laminar corium, using a carbohydrate-overload model in ponies to trigger acute disease. Their comprehensive approach combined haemostatic profiling (platelet counts, survival, and clotting times), nuclear scintigraphy using indium-111–labelled platelets to visualise thrombosis in vivo, contrast arteriography to assess perfusion, and histopathological examination of affected laminae. The researchers found that whilst platelet numbers remained stable, platelet survival shortened significantly and radioactive platelets accumulated in the distal hoof wall; crucially, microthrombi were identified in dermal veins of three of four affected ponies at the onset of lameness, accompanied by evidence of systemic coagulopathy (shortened recalcification time early, followed by prolonged activated clotting time). Microvascular blood flow was markedly reduced in affected feet despite unchanged systemic platelet counts, suggesting that localised thrombotic events rather than systemic platelet depletion drive the vascular compromise. For practitioners, these findings provide direct evidence supporting a thrombotic mechanism in laminitis pathogenesis, raising questions about whether anticoagulant or antiplatelet therapies might be beneficial during the critical early phase, and underscoring the importance of addressing underlying triggers (such as feed-related causes) that appear to precipitate the coagulopathic cascade.
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Practical Takeaways
- •Microvascular thrombosis is a documented pathophysiological mechanism in acute laminitis, suggesting that anticoagulant or antiplatelet therapies may have therapeutic potential
- •Systemic coagulopathy changes occur before clinical lameness appears, indicating early intervention during the prodromal phase may be critical
- •Carbohydrate overload triggers measurable hemostatic alterations that precede and likely contribute to the thrombotic events causing laminar tissue damage
Key Findings
- •Microvascular thrombosis was present in the laminar dermis of affected feet in 3 of 4 ponies with laminitis at onset of lameness
- •Platelet survival was shortened and 111In-labeled platelets accumulated distal to the coronary band in affected feet
- •Arteriography revealed marked reduction in blood supply to affected hooves compared to controls
- •Whole blood recalcification time shortened at 8 hours post-carbohydrate but prolonged at lameness onset, indicating systemic coagulopathy preceded thrombosis formation