Arteriosclerosis
Encompasses a group of diseases characterised by degeneration of the arterial walls with fibrous thickening. The disease is chronic and non-inflammatory. As the vessels lose their elasticity the lumen becomes narrowed and the end result is ischaemia if the tissue bed supplied.
Incidence:
- Horse: mainly in the aorta and branch points of arteries.
- Dog: commonly seen in th myocardium. Contributes to myocardial scarring and damage preceding myocardial failure.
- Also occurs in cattle.
Thought to be aetiologically related to haemodynamic damage to the endothelial layer. Perhaps initiated by:
- Platelet endothelial interaction.
- Plasma constituents entering the sub-endothelial layer.
Changes may be:
Hyperplastic
Chronically raised intraluminal pressure stimulates hyperplasia of the smooth muscle layer, reducing the size of the vessel lumen. The elastic lamina may become duplicated or split allowing penetration of hyperplastic smooth muscle cells into the intima. Fibrous plaques form.
Hyaline
May occur alongside hyperplastic lesions or alone as a primary lesion. The intima becomes more permeable, allowing penetration of plasma contents into the vessel wall which becomes degenerate.
A combination of hyerplastic and hyaline change is often seen in the coronary arteries of the dog. Associated with ischaemic necrosis of the myocardium and therefore heart failure.
Also seen in uterine and ovarian arteries of pregnant animals. Thought to be clinically insignificant but indicated raised intraluminal pressure.
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