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Heart Center Virtual Tour

Coronary artery disease - Introduction

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of coronary artery disease (CAD).

Alternative Names

Angina; Atherosclerosis; Heart disease

Introduction:

According to a 2007 report, nearly 16 million Americans have coronary artery disease (CAD). In the U.S., coronary artery disease is the leading killer of both men and women. Each year, nearly 500,000 people die because of CAD. On the positive side, heart attack mortality rates have been declining. Half of men and 63% of women who die of heart disease do not have angina or other warning symptoms prior to their fatal attacks. Although at this time no tests can reliably predict whether a heart attack will occur, experts estimate that up to 30% of fatal attacks and many follow-up surgeries could be avoided with healthy lifestyle changes and by sticking to medical treatments. Two-thirds of patients who have suffered a first heart attack, however, do not take the necessary steps to prevent another.

The heart is the human body's hardest working organ. Throughout life it continuously pumps blood enriched with oxygen and vital nutrients through a network of arteries to all tissues of the body.

The external structures of the heart include the ventricles, atria, arteries, and veins. Arteries carry blood away from the heart while veins carry blood into the heart. The vessels colored blue indicate the transport of blood with relatively low content of oxygen and high content of carbon dioxide. The vessels colored red indicate the transport of blood with relatively high content of oxygen and low content of carbon dioxide.

To perform the difficult task of pumping blood to the rest of the body, the heart muscle itself needs a plentiful supply of oxygen-rich blood, which is provided through a network of coronary arteries. These arteries carry oxygen-rich blood to the heart's muscular walls (the myocardium).

Click the icon to see an image of the anterior heart arteries.

If blood flow to the myocardium is interrupted, an injury known as an infarct occurs. This is called myocardial infarction or, more commonly, a heart attack.

Click the icon to see an animation about coronary artery disease.

The Process of Atherosclerosis

Coronary artery disease is the end result of a complex process known as atherosclerosis (commonly called "hardening of the arteries"). This causes blockage of arteries (ischemia) and prevents oxygen-rich blood from reaching the heart. There are many steps in the process leading to atherosclerosis, some not fully understood.

Click the icon to see an image of atherosclerosis.

Increasingly, however, researchers are studying the interactions between cholesterol and processes known as oxidation and the inflammatory response.

Cholesterol and Lipoproteins. The story begins with cholesterol and sphere-shaped bodies called lipoproteins that transport cholesterol.

Cholesterol is a white, crystalline substance found in all animal cells and animal-based foods. It is critical for many functions, but under certain conditions cholesterol can have ge harmful.
The lipoproteins that transport cholesterol are referred to by their size. The most commonly known are low-density lipoproteins (LDL) and high density lipoproteins (HDL). LDL is often referred to as the "bad" cholesterol and HDL as the "good" cholesterol.

Click the icon to see an image of cholesterol inside an artery.

Oxidation. The damaging process called oxidation is an important trigger in the atherosclerosis story.

Oxidation is a chemical process in the body caused by the release of unstable particles known as oxygen-free radicals. It is one of the normal processes in the body, but under certain conditions (such as exposure to cigarette smoke or other environment stresses) these free radicals are overproduced.
In excess amounts, they can be very dangerous, causing damaging inflammation and even affecting genetic material in cells.
In heart disease, free radicals are released in artery linings and oxidize low-density lipoproteins (LDL). The oxidized LDL is the basis for cholesterol build-up on the artery walls and damage leading to heart disease.

Inflammatory Response. For the arteries to harden there must be a persistent reaction in the body that causes ongoing harm. Researchers now believe that this reaction is an immune process known as the inflammatory response.

Click the icon to see an image of atherosclerosis.

Thre is growing evidence that the inflammatory response may be present not only in local plaques in single arteries but also throughout the arteries leading to the heart.

Blockage in the Arteries. Eventually these calcified (hardened) arteries become narrower (a condition known as stenosis).

As this narrowing and hardening process continues, blood flow slows, preventing sufficient oxygen-rich blood from reaching the heart muscles.
Such oxygen deprivation in vital cells is called ischemia. When it affects the coronary arteries, it causes injury to the tissues of the heart.
These narrow and inelastic arteries not only slow down blood flow but also become vulnerable to injury and tears.

Click the icon to see an image of coronary artery blockage

The End Result: Heart Attack. Heart attack can occur as a result of one or two effects of atherosclerosis.

If the artery becomes completely blocked and ischemia becomes so extensive that oxygen-bearing tissues around the heart die.
If the plaque itself develops fissures or tears. Blood platelets adhere to the site to seal off the plaque, and a blood clot (thrombus) forms. A heart attack can then occur if the formed blood clot completely blocks the passage of oxygen-rich blood to the heart.

Click the icon to see an image of the developmental process of atherosclerosis.

Resources

www.nhlbi.nih.gov -- National Heart, Lung, and Blood Institute
www.americanheart.org -- American Heart Association
www.acc.org -- American College of Cardiology

References

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Reviewed last on: 4/17/2008
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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