Atherosclerosis

Definition

Definition of Atherosclerosis
Atherosclerosis (also known as arteriosclerotic vascular disease or ASVD) is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol. It is a syndrome affecting arterial blood vessels, a chronic inflammatory response in the walls of arteries, caused largely by the accumulation of macrophage white blood cells and promoted by low-density lipoproteins (plasma proteins that carry cholesterol and triglycerides) without adequate removal of fats and cholesterol from the macrophages by functional high density lipoproteins (HDL), (see apoA-1 Milano). 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.

Symptoms

Symptoms of Atherosclerosis
Atherosclerosis does not occur in children, but can begin forming as early as the teen years. Until progressing to an advanced stage, it is usually asymptomatic. Atheroma in arm, or more often in leg arteries, which produces decreased blood flow is called peripheral artery occlusive disease (PAOD). Typically, atherosclerosis begins as a thin layer of white streaks on the artery wall (usually due to white blood cells) and progresses from there.

According to United States data for the year 2004, for about 66% 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 illustration above, like most illustrations of arterial disease, overemphasizes lumen narrowing, as opposed to compensatory external diameter enlargement (at least within smaller arteries, e.g., heart arteries) typical of the atherosclerosis process as it progresses (see Glagov or the ASTEROID trial). The relative geometry error within the illustration is common to many older illustrations, an error slowly being more commonly recognized within the last decade.

Causes

Causes of Atherosclerosis
The main cause of atherosclerosis is yet unknown, but is hypothesized to fundamentally be initiated by inflammatory processes in the vessel wall in response to retained low-density lipoprotein (LDL) molecules. Once inside the vessel wall, LDL molecules become susceptible to oxidation by free radicals, and become toxic to the cells. The damage caused by the oxidized LDL molecules triggers a cascade of immune responses which over time can produce an atheroma. The LDL molecule is globular shaped with a hollow core to carry cholesterol throughout the body.

The body's immune system responds to the damage to the artery wall caused by oxidized LDL by sending specialized white blood cells (macrophages and T-lymphocytes) to absorb the oxidized-LDL forming specialized foam cells. These white blood cells are not able to process the oxidized-LDL, and ultimately grow then rupture, depositing a greater amount of oxidized cholesterol into the artery wall. This triggers more white blood cells, continuing the cycle.

Diagnosis

Diagnosis of Atherosclerosis
Areas of severe narrowing, stenosis, detectable by angiography, and to a lesser extent "stress testing" have long been the focus of human diagnostic techniques for cardiovascular disease, in general. However, these methods focus on detecting only severe narrowing, not the underlying atherosclerosis disease. As demonstrated by human clinical studies, most severe events occur in locations with heavy plaque, yet little or no lumen narrowing present before debilitating events suddenly occur. Plaque rupture can lead to artery lumen occlusion within seconds to minutes, and potential permanent debility and sometimes sudden death.

Plaques that have ruptured are called complicated plaques. The extracellular matrix of the lesion breaks, usually at the shoulder of the fibrous cap that separates the lesion from the arterial lumen, exposing thrombogenic material, mainly collagen, and eventually causing thrombus formation. This thrombus will eventually grow and travel downstream until eventually occluding a narrow artery. Once the area is blocked, blood and oxygen will not be able to supply the vessels and will cause death of cells and lead to necrosis and poisoning. Serious complicated plaques can cause death of organ tissues, causing serious complications to that organ system.

Greater than 75% lumen stenosis used to be considered by cardiologists as the hallmark of clinically significant disease because it is typically only at this severity of narrowing of the larger heart arteries that recurring episodes of angina and detectable abnormalities by stress testing methods are seen. However, clinical trials have shown that only about 14% of clinically debilitating events occur at locations with this, or greater severity of stenosis. The majority of events occur due to atheroma plaque rupture at areas without narrowing sufficient enough to produce any angina or stress test abnormalities. Thus, since the later-1990s, greater attention is being focused on the "vulnerable plaque."

Treatment

Treatment of Atherosclerosis
To help prevent hardening of the arteries, make the following lifestyle changes:

1. Avoid fatty foods. Eat well-balanced meals that are low in fat and cholesterol. Include several daily servings of fruits and vegetables. Adding fish to your diet at least twice a week may be helpful. However, do not eat fried fish.
2. Limit how much alcohol you drink - one drink a day for women, two a day for men.
3. Exercise for 30 minutes a day if you are not overweight, and for 60 - 90 minutes a day if you are overweight.

Quit smoking: This is the single most important change you can make to reduce your risk of heart disease and stroke.

Get your blood pressure checked every 1 - 2 years before age 50 and yearly after age 50. Have your blood pressure checked more often if you have high blood pressure, heart disease, or you have had a stroke. Talk to your doctor about how often you should have your blood pressure checked.

If your blood pressure is high, it is important for you to lower it and keep it under control.

1. Everyone should keep their blood pressure below 140/90 mmHg
2. If you have diabetes, kidney disease, or have had a stroke or heart attack, your blood pressure should probably be less than 130/80 mm/Hg. Ask your doctor what your blood pressure should be.

Prognosis

Prognosis of Atherosclerosis
Improved treatments have reduced the number of deaths from atherosclerosis-related diseases. These treatments also have improved the quality of life for people who have these diseases. However, atherosclerosis remains a common health problems.

Prevention

Prevention of Atherosclerosis
You may be able to prevent or delay atherosclerosis and the diseases it can cause. Making lifestyle changes and getting ongoing care can help you avoid the problems of atherosclerosis and live a long, healthy life.