Atherosclerosis

Altherosclerosis

Diseases caused by atherosclerosis are the leading cause of illness and death for both men and women in the U.S, according to the National Heart, Lung, and Blood Institute. Although breast cancer is often the illness most feared by women, the disease affects one out of nine women over the lifetime, compared to coronary heart disease, which affects one out of every two women over the lifetime. Atherosclerosis is often the first stage of coronary heart disease (CHD).

Often referred to as "hardening of the arteries," atherosclerosis occurs when your arteries narrow and become less flexible. This happens when cholesterol, fatty substances, cell waste products, calcium and fibrin—collectively called plaque—collect on the inner walls. The arteries respond to the buildup by becoming inflamed, which, in turn, results in the formation of scar tissue and the collection of other cells in the affected areas, further narrowing the artery.

Atherosclerosis can affect medium and large arteries anywhere in your body. If someone has atherosclerosis in one part of their body, they typically will also have atherosclerosis in other parts of their bodies. Atherosclerosis restricts blood flow, thus limiting the amount of oxygen available to your organs. When blood flow to the heart is reduced, for instance, chest pain, or angina, may result. Similarly, when blood flow to the arteries in the legs is reduced, leg pain called claudication may result.

As the disease progresses, atherosclerosis can completely clog arteries, cutting off blood flow. This usually happens suddenly when a blood clot forms in the damaged arteries on top of the atherosclerosis. This is especially dangerous in arteries near the brain, heart or other vital organs. If blood flow to the heart is nearly or completely blocked, a heart attack results and muscle cells in the heart die. The result is permanent heart damage. Similarly, if blood flow is abruptly cut off to the brain, this can cause a stroke, which may also result in permanent brain damage. And if blood flow is abruptly cut off to the legs, the leg may have to be amputated. Thus atherosclerosis can lead to serious life-threatening complications if not addressed early through prevention and early treatment.

Atherosclerotic plaques have a cholesterol- or lipid-rich core covered by a fibrous cap. If this cap ruptures, it exposes this lipid-rich core to blood. The sticky core attracts platelets, forming a blood clot, called a thrombus, at the site. This clot can completely clog the artery and cut off blood flow.

More mature plaques (stable plaques) have a thick fibrous cap, which is less likely to rupture. Softer, fattier plaques (unstable plaques) have a weaker cap and are more likely to rupture.

Two thirds of sudden total or near total blockage (called an occlusion) develops in arteries that were less than 50 percent narrowed, and 97 percent of plaque rupture occurs in arteries with less than 70 percent narrowing.

So the degree of narrowing in a particular artery does not necessarily predict complete blockage in that same artery.

Tighter or narrower arteries may cause angina, but are not necessarily more likely to rupture. However, the total amount of plaque or atherosclerosis in all your arteries predicts your risk of a heart attack.

We don't know what causes plaque to begin building up in arteries. Some experts think plaque begins to accumulate in places where the inner layer of an artery is damaged.

The specific arteries most at risk for atherosclerosis-induced blockage are those going to your brain (carotid), heart (coronary) and legs (femoral or iliac). Atherosclerosis in the legs is the most common form of peripheral arterial disease (PAD) and can lead to intermittent claudication—severe pain, aching or cramping when walking, numbness, reduced circulation, and if left untreated, gangrene (death of tissue).

Risk Factors for Atherosclerosis:

Over the last two decades, researchers have identified many risk factors for developing cardiovascular diseases. They include:

• Elevated cholesterol levels (both total cholesterol and LDL ("bad") cholesterol)
• Elevated triglyceride levels
• High blood pressure hypertension
• Cigarette smoke
• Low HDL cholesterol (the "good" cholesterol that clears away artery-clogging LDL cholesterol—the "bad" cholesterol)
• Diabetes (elevated blood sugar)
• Advanced age

Age

Generally, women over age 55 and men over age 45 are at greatest risk for developing atherosclerosis. The risk of cardiovascular events increases with age.

Global Risk Factor Assessment

The Framingham Risk Score is a useful, office-based risk prediction model. It assigns a point score for each major risk factor to predict your 10-year risk of developing future cardiovascular events. You can estimate your own 10-year risk at: http://hp2010.nhlbihin.net

If you have more than a 20 percent risk of future cardiac events over the next 10 years, you should be treated very aggressively, the same as someone with known heart disease. Intermediate risk individuals with scores between 10 percent and 20 percent should have further risk evaluation. Low-risk individuals with scores of less than 10 percent usually don't need drug therapy, but should make lifestyle changes such as diet and exercise, which are recommended for everyone.

Other risk factors for coronary heart disease include:

• A family history of early heart disease
• Obesity
• Metabolic syndrome
• Physical inactivity and sedentary lifestyle
• Postmenopausal status
• High levels of homocysteine
• Family History

Even though it is not included in the Framingham Risk Score, family history is one of the biggest risk factors overall for atherosclerosis. Your risk is greater if your father or brother was diagnosed before age 55, if your mother or sister was diagnosed before age 65, or if you have a sibling with early coronary disease.

Post-menopausal status

A woman's risk of developing atherosclerosis and heart disease increases once she reaches menopause. Prior to menopause, women are mainly protected from heart disease by estrogen, the reproductive hormone produced by the ovaries. This protection is why women tend to develop heart disease 10 years after men. However this 10-year protection is not seen in women who smoke or those with diabetes.

Among its many roles, estrogen helps keep arteries free from plaque by improving the ratio of LDL (low-density lipoprotein) and HDL (high-density lipoprotein) cholesterol. It also increases the amount of HDL cholesterol, which helps clear arteries of LDL cholesterol—the kind that most contributes to plaque build up.

Estrogen also helps keep the lining of your blood vessels strong and pliable, which helps reduce your risk of atherosclerosis. Despite the theoretical benefits of estrogen, replacing natural estrogen hormones with drugs after menopause is not an effective way to prevent heart disease, and may even be harmful.