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Coronary Artery Disease - An Overview

A review of the common manifestations of CAD

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Updated December 29, 2005

By DrRich

Updated January, 2006

The coronary arteries are the blood vessels that supply oxygen and nutrients to the heart muscle, and when they become diseased, the heart muscle is at great risk. Coronary artery disease (CAD) is the single largest killer of American women (and men). In 2001, almost 250,000 American women died from CAD.

"Typical" CAD

CAD occurs when part of the smooth, elastic lining inside a coronary artery develops atherosclerosis. With atherosclerosis, the artery's lining becomes hardened, stiffened, and swollen with all sorts of "grunge" - including calcium deposits, fatty deposits, and abnormal inflammatory cells - to form a plaque. Plaques can be thought of as large "pimples" that protrude into the channel of an artery, causing a partial obstruction to blood flow. Patients with CAD might have just one or two plaques, or might have dozens distributed throughout their coronary arteries.

Angina

If a plaque becomes large enough, under conditions of exercise or stress it may prevent the heart muscle from receiving all the blood it needs. The symptoms caused by the oxygen-starved heart muscle is called angina. Angina typically is felt as "heavy" left-sided chest pain, most often pressure-like in character, which can radiate to the jaw or left arm. Usually angina is relieved within a few minutes by resting.

Myocardial infarction (MI,) or heart attack

Sometimes a plaque will suddenly rupture. Blood is then exposed to the "grunge" inside the plaque, and begins to clot; soon the clot blocks the artery. The portion of heart muscle supplied by the occluded artery starts to die, and unless blood flow is restored within a few hours, the damage to the heart muscle becomes permanent. This event (permanent heart muscle damage caused by an occluded coronary artery) is called a myocardial infarction (MI,) or heart attack.

The symptoms of an acute MI usually are similar to those of angina, but are much more severe and persistent, and are often accompanied by lightheadedness, nausea, sweating, and a sense of impending doom. If the patient survives the MI itself, the resulting heart muscle damage can lead to chronic heart failure or fatal heart rhythm disturbances.

Unstable angina

Unlike typical angina, unstable angina most often occurs at rest. It is usually caused by small transient blood clots forming at the site of a partially-ruptured plaque. When the clot forms, angina occurs; when the clot dissolves the angina disappears. The main differences between unstable angina and an acute MI are that in unstable angina the clot does not fully occlude the artery, and the episode is transient. Indeed, unstable angina can be thought of as a self-terminating MI. Unstable angina frequently presents as a series of attacks, and if untreated will often culminate in a true MI. This condition is a medical emergency - treatment is very similar to that for an acute MI (see below.)

Diagnosing CAD

Noninvasive testing: Exercise testing (or stress testing) is often helpful in diagnosing CAD. If exercise reproduces the patient's angina and if typical changes are seen on the electrocardiogram (ECG,) the diagnosis of CAD can be made with some confidence.

When added to a stress test, an echocardiogram or a thallium study can improve its diagnostic accuracy. The echocardiogram creates an image of the beating heart using sound waves. Any abnormal movement in the heart muscle during exercise suggests CAD. Thallium is a radioactive substance that is injected into a vein during exercise, and is distributed to the heart muscle by the coronary arteries, thus allowing the heart to be imaged. Portions of the heart muscle fed by partially blocked coronary arteries show up as dark spots.

Invasive testing: If noninvasive testing suggests the presence of significant CAD, coronary angiography is often performed. In this test, catheters are positioned within the coronary arteries and dye is injected. X-rays are then taken to visualize the arteries and localize any blockages. Coronary angiography is considered the "gold standard" for diagnosing CAD.

Next - The treatment of coronary artery disease

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