Heart health

Saturday 05 December 2009, 03:04

Atherosclerosis: what is it?

The pathogenetic process of atherosclerosis

Atherosclerosis: what is it?

Atherosclerosis is a chronic progressive inflammatory disease affecting arterial walls (especially coronary artery walls) and potentially leading to the occurrence of acute cardiovascular events, such as myocardial infarction, angina pectoris and sudden cardiac death.


Atherosclerosis is preceded by a long asymptomatic phase, called subclinical atherosclerosis, where the formation of fatty plaques (atheromas) in the walls of arteries begins. Atheroma formation (atherogenesis) begins at an early age and progresses throughout life. It starts at sites of pre-existing endothelial injury resulting from a variety of causes (such as hypertension, high plasma levels of LDL cholesterol, low plasma levels of HDL cholesterol, diabetes, chemical substances in cigarette smoke) and leads to the formation of fatty plaques on the inside walls of the arteries.


In early atherosclerotic lesions, plaques are made up of modified LDL cholesterol and other lipids, initially deposited in the extracellular space and then accumulated by macrophages (foam cells). As lesion progresses, T-lymphocytes infiltrate the developing lesions and secrete inflammatory cytokines and growth factors, which in turn stimulate the surrounding fibrous and smooth muscle tissue to proliferate and form larger and larger plaques.


In advanced atherosclerotic lesions, plaques can become so large that they can protrude into the arterial lumen, narrowing it even to occlusion. Moreover, the progressive deposition of fibrous tissue leads to the stiffening of arterial walls, which in turn is responsible for increased pulse pressure and altered coronary perfusion.


The stability of advanced plaques depends on their composition. As a general rule, plaques with small lipid cores, few inflammatory cells and great amounts of fibrous and smooth muscular tissue are stable. On the contrary, plaques with large lipid cores, numerous macrophages and small amounts of fibrous and smooth muscular tissue are prone to rupture.


Plaque rupture is always a critical event. It always results in the formation of thrombi that, when sufficiently large, can occlude the coronary vessel lumen and lead to myocardial infarction and even sudden cardiac death.


By Chiara De Carli

Category: Heart health

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