Blood vessels Blood vessels

Arteriosclerosis of intramural coronary arteries has been reported to occur in 77.6% of geriatric dogs over 12 years of age (Valtonen 1972), 60% of dogs over 14 years of age (Detweiler et al. 1968) and 50% of dogs aged 13 years or older (Jonsson 1972). A direct association was found between the presence of arteriosclerosis and microscopic intramural myocardial infarcts (MIMIs).

These structural changes cause a loss of elasticity of vascular walls and / or luminal narrowing, and contribute to increased peripheral resistance which, combined with reduced sensitivity to the vasodilator effect of b-adrenergic stimulation (see below), probably contributes to the increased aortic impedance and left ventricular afterload seen in geriatric patients.

Vessels supplying various organs throughout the body may be affected, notably the kidney and brain, resulting in impaired vascular supply, and ultimately impaired organ function.

Atherosclerosis leading to myocardial infarction while common in humans is rare in dogs and cats. Obesity and thyroid atrophy or frank hypothyroidism are associated with the development of atherosclerosis in geriatric dogs. Experimentally, atherosclerosis can only be caused in hypothyroid dogs on high fat diets. Miniature schnauzers with hyperlipidaemia may be predisposed to develop atherosclerosis.