The types and definitions of arteriosclerosis were described in January of 1954 in the American Journal of Clinical Pathology by S. M. Rabson titled, “Arteriosclerosis: Definitions”. He said that atherosclerosis is defined as arteriosclerosis with atheromatosis.

At present arteriosclerosis or arterial stiffness is classified into three lesions:-

• Atherosclerosis – Atherosclerosis affects the elastic and large arteries in which there is atheroma formation.
• Moenckeberg medial calcific sclerosis
• Arteriolosclerosis

Pathology

The arteriosclerosis lesions begin as the intima in the arterial wall starts to enlarge with the deposition of variable amounts and types of lipids, inflammatory cells, connective tissues as well as matrix proteins, enzymes and calcium deposits.

As these lesions mature, they are called atherosclerosis. Atherosclerosis is atheroma with arteriosclerosis. This is the largest killer in industrialized countries leading to hundreds of thousands of heart attacks and strokes.

There are several subclassifications of atherosclerosis including one adopted by the American Heart Association.

Moenckeberg medial calcific sclerosis is the deposition of calcium in the tunica media of the large and medium sized arteries. It is rarely seen in patients younger than 50 years.
 

This type of calcification affects only the walls and does not affect the lumen of the arteries unlike atherosclerosis. Moenckeberg sclerosis and atherosclerosis may occur together where both the wall and lumen may be affected.

Arteriolosclerosis affects small arterial vessels with 1 or 2 layers of smooth muscle cells in their walls only called arterioles. However, the condition affects arterioles throughout the body and is common among those with high blood pressure (hypertension) and diabetes mellitus.

Arteriosclerosis subtypes

Pathologically there are two subtypes of arteriosclerosis:-

• hyperplastic type
• hyaline type

A subclassification of arteriolosclerosis is the fibromuscular intimal thickening. There is typically hyalinosis or deposition of hyaline protein in these lesions as well. This includes the categories like:-

• transplant related arteriopathy or arterial damage
• restenosis lesions that are seen after balloon angioplasty or stenting of the heart’s coronary blood vessels
• nonspecific intimal thickening as occurs in temporal arteries (arteries around the forehead and temples) with aging.

Transplant arteriopathy is intimal enlargement without atherosclerotic changes seen in the walls. Transplant arteriopathy affects large and small muscular arteries and veins as well. It commonly causes inflammation in the 1 or more of the 3 layers in the blood vessel walls. 

Usually, the intima is affected more than the media or adventitia, but all three layers may be affected. After inflammation there is fibrosis and finally calcification and thrombosis may occur.