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Revision as of 06:41, 24 July 2007 by 210.4.37.47 (talk)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff) Medical condition| Atherosclerosis | |
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| Specialty | Cardiology  |
Atherosclerosis is a disease affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part to the deposition of lipoproteins (plasma proteins that carry cholesterol and triglycerides). It is commonly referred to as a "hardening" or "furring" of the arteries. It is caused by the formation of multiple plaques within the arteries.
Pathologically, the atheromatous plaque is divided into three distinct components:
- The atheroma ("lump of porridge", from Athera, porridge in Greek,) is the nodular accumulation of a soft, flaky, yellowish material at the center of large plaques, composed of macrophages nearest the lumen of the artery.
- Underlying areas of cholesterol crystals.
- Calcification at the outer base of older/more advanced lesions.
The following terms are similar, yet distinct, in both spelling and meaning, and can be easily confused: arteriosclerosis, arteriolosclerosis and atherosclerosis. Arteriosclerosis is a general term describing any hardening (and loss of elasticity) of medium or large arteries (in Greek, "Arterio" meaning artery and "sclerosis" meaning hardening), arteriolosclerosis is arteriosclerosis mainly affecting the arterioles (small arteries), atherosclerosis is a hardening of an artery specifically due to an atheromatous plaque. Therefore, atherosclerosis is a form of arteriosclerosis.
Arteriosclerosis ("hardening of the artery") results from a deposition of tough, rigid collagen inside the vessel wall and around the atheroma. This increases the stiffness, decreases the elasticity of the artery wall. Arteriolosclerosis (hardening of small arteries, the arterioles) is the result of collagen deposition, but also muscle wall thickening and deposition of protein ("hyaline").
Calcification, sometimes even ossification (formation of complete bone tissue) occurs within the deepest and oldest layers of the sclerosed vessel wall.
Atherosclerosis causes two main problems. First, the atheromatous plaques, though long compensated for by artery enlargement, eventually lead to plaque ruptures and stenosis (narrowing) of the artery and, therefore, an insufficient blood supply to the organ it feeds. Alternatively, if the compensating artery enlargement process is excessive, then a net aneurysm results.
These complications are chronic, slowly progressing and cumulative. Most commonly, soft plaque suddenly ruptures (see vulnerable plaque), causing the formation of a thrombus that will rapidly slow or stop blood flow, e.g. 5 minutes, leading to death of the tissues fed by the artery. This catastrophic event is called an infarction. One of the most common recognized scenarios is called coronary thrombosis of a coronary artery causing myocardial infarction (a heart attack). Another common scenario in very advanced disease is claudication from insufficient blood supply to the legs, typically due to a combination of both stenosis and aneurysmal segments narrowed with clots. Since atherosclerosis is a body wide process, similar events also occur in the arteries to the brain, intestines, kidneys, legs, etc.
Symptoms
Atherosclerosis typically begins in early adolescence, and is usually found in most major arteries, yet is asymptomatic and not detected by most diagnostic methods during life. Autopsies of healthy young men who died during the Korean and Vietnam Wars showed evidence of the disease. It most commonly becomes seriously symptomatic when interfering with the coronary circulation supplying the heart or cerebral circulation supplying the brain, and is considered the most important underlying cause of strokes, heart attacks, various heart diseases including congestive heart failure and most cardiovascular diseases in general. Atheroma in arm or more often leg arteries and producing decreased blood flow is called Peripheral artery occlusive disease (PAOD).
According to United States data for the year 2004, for about 65% of men and 47% of women, the first symptom of atherosclerotic cardiovascular disease is heart attack or sudden cardiac death (death within one hour of onset of the symptom).
Most artery flow disrupting events occur at locations with less than 50% lumen narrowing (~20% stenosis is average. The relative geometry error within the illustration is common to many older illustrations, an error slowly being more commonly recognized within the last decade.
Cardiac stress testing, traditionally the most commonly performed non-invasive testing method for blood flow limitations generally only detects lumen narrowing of ~75% or greater, although some physicians advocate that nuclear stress methods can detect as little as 50%.