Arteriosclerosis

What is Arteriosclerosis?

Arteriosclerosis is defined as stiffening or hardening or the arterial walls.

Arteries are blood vessels that carry healthy, oxygen and nutrient rich blood to the various peripheral organs of the body. As the arterial walls harden, the heart has to pump harder and against a greater resistance to enable that the arterial blood reaches all the peripheral organs.

History of arteriosclerosis

The name arteriosclerosis is derived from the Greek words meaning “hardening of the arteries.” Arteriosclerosis is a phenomenon that may have existed since ancient times even in Egypt. It was not until the 20th Century however that the word and its clinical implications became known.

It was in 1575 that Fallopius wrote of a condition where arteries degenerated into bones. The anatomists of that time noted these ossified arteries or arteries that had hardened into bone like structures.

Johann Friedrich Crell, in 1740 said that this hardening was not due to ossification of turning into bone but due to pus.

von Haller in 1755 found that these lesions that Crell thought were pus were actually something else. He named them atheroma that in Greek meant a space filled with gruel like matter.

The term arteriosclerosis was first used by Jean Fréderic Martin Lobstein while he analyzed the composition of calcified arterial lesions.

George Johnson described in his review on Bright disease in 1868 the noncalcified, nonatheromatous stiffening of small vessels. Gull and Sutton thereafter described arterio-capillary fibrosis that went on to be called arteriosclerosis.

Types and pathology of arteriosclerosis

Despite being used interchangeably arteriosclerosis is described under three headings – atherosclerosis, Moenckeberg medial calcific sclerosis and arteriolosclerosis. These lesions have three common features including stiffening of arterial vessels, thickening of the arterial wall and degenerative nature of the disease.

Risks and complications associated with arteriosclerosis

Those with arteriosclerosis commonly suffer from hypertension or high blood pressure.

Commonly arteriosclerosis progresses to atherosclerosis and its complications. These include coronary artery disease, when the atherosclerotic plaques occur in the arteries of the heart. This may lead to angina (chest pain on exertion), arrhythmias (abnormal heart rates or rhythms) etc.

Another complication of atherosclerosis is cerebrovascular disease (that raises the risk of stroke or a transient ischemic attack) and peripheral artery disease (PAD) that is progressive hardening and narrowing of the arteries in the legs and arms.

Arteriosclerosis Types

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.