Muscle Ischaemia
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- Firstly segmental necrosis
- -> death of satellite cells
- Causes regeneration but myoblast precursors have to be recruited from viable fibres
- -> death of all cells
- Mostly healed by fibrosis and scar formation
- May attempt regeneration by budding
Main causes:
- Vascular occlusion
- Infarction from embolism is rare due to collateral circulation
- Extension of infarcts depends on size of vessels occluded
- Small capillaries -> segmental necrosis
- Large arteries -> whole muscle areas, including sattelite cells, are killed
- Healed by fibrosis
- May be due to:
- Blockage of iliac arteries by aortic-iliac thrombosis in horses
- Blockage of aortic bifurcation in cats
- Dirofilaria immitis arteritis in dogs
- Vasculitis due to bluetongue virus in sheep
- Equine purpura haemorrhagica
- Non-contagious, sporadic
- Grossly:
- Subcutaneous oedema
- Scattered haemorrhagic foci throughout skin and muscles
- Vasculitis -> infarcts of muscles
- May cause myoglobinuria if extensive
- Possibly immune mediated
- In horses post streptococal infection, especially strangles
- External pressure
- During prolonged recumbency, e.g. anaesthesia, inability to rise, or due to too tightly fitting bandages or casts
- Post anaesthesia myopathy especially in horses
- Dorsal recumbancy -> gluteals and longissimus ischaemia
- Lateral recumbancy -> triceps brachii, pectoralis, deltoideus and brachiocephalicus ischaemia
- Caused by pressure on muscle > perfusion pressure of capillaries
- Downer cows - vetral recumbency -> ischaemia of pectoral muscles and muscles of limbs tucked under the animal
- Pregnant ewes with twins or triplets -> internal abdominal oblique muscle ischaemic necrosis -> potential rupture
- Muscle swelling where it cannot expand
- E.g. supracoracoid muscle infarction in some breeds of turkeys after flapping their wings
- Surrounded by inelastic fascial sheath and bone
- E.g. supracoracoid muscle infarction in some breeds of turkeys after flapping their wings