What is coronary artery disease?

Inflammation and CAD

Genes and CAD

Fats—the bad and the good

1. An angina attack usually strikes when a partial blockage in one or more coronary arteries restricts blood flow to the heart.
   
   
2. Blockages are a result of coronary artery disease (CAD), which is caused by fatty deposits building up on the walls of the arteries of the heart—a condition known as atherosclerosis.
   
   
3. When the arteries of the heart have fat and cholesterol build up on the artery wall, the body’s immune system sends cells to fight the injury, and the area becomes inflamed. This can lead to heart attacks.
   
   
4. Fats, mainly cholesterol and triglycerides, are the main culprits in plaque production.
   
   

An angina attack usually strikes when a partial blockage in one or more coronary arteries restricts blood flow to the heart. Deprived of oxygen, the heart works too hard, leading to the chest pain or discomfort that you recognize as an angina attack.

There are three main coronary arteries in the heart. The left anterior descending artery is usually the largest artery and supplies blood to the left ventricle and the front of the heart. Because this artery is so large and has many branches delivering blood to such an important area, a blockage in this artery may have severe results.

Blockages are a result of coronary artery disease (CAD). CAD is also called ischemic heart disease (IHD). Other names are coronary atherosclerosis and coronary arteriosclerosis.

All of these names mean basically the same thing: excessive fats in the blood are causing arteries in the heart to gradually narrow and harden, resulting in less oxygen-rich blood for the heart. Hyperlipidemia can increase your risk of having heart disease and stroke.¹ Therefore, it is important to try to reduce the level of fats in your bloodstream. Even small reductions in the amount of these fats can greatly reduce your risk of CAD.² However, other factors such as high blood pressure and smoking can also increase your risk for getting CAD. Eating well and exercising can help reduce it. Learn more in Risk Factors, Nutrition Matters, and Exercise for Heart Health.

A coronary artery partially blocked with plaque. Click here to enlarge.

Simply put, CAD is caused by a buildup of fatty deposits called plaques on the walls of the three main and the smaller coronary arteries, a condition known as atherosclerosis (hardening of the arteries). Imagine how the buildup in the drainpipe below your kitchen sink reduces water flow and you have a pretty good idea of what happens in your coronary arteries.

Plaques can take years to develop and cause angina symptoms. The more fats you have traveling in your bloodstream, the more likely they will attach to the artery wall.

Over time, as plaque buildup becomes larger, the open space in the arteries becomes more narrow, reducing the flow of blood and oxygen to the heart. The result? Possibly an angina attack.

The combination of CAD and angina can, unfortunately, lead to additional heart problems later if left untreated. See When Angina Gets Worse for more.

When excess fat and bad cholesterol build up in the walls of the arteries of the heart, the body’s immune system sends cells to fight the injury, and the area becomes inflamed or swollen. Unfortunately, this swelling may actually make the problem worse by allowing the plaque to grow and making it easier for blood clots to form.³

As the body’s defense cells gather at the site of injury, the plaque gets bigger. Sometimes a ‘fibrous cap’ forms over the top of the plaque, holding the cells together and making it even larger. However, as the inflammation continues, the plaque can weaken and eventually break (or ‘rupture’).

When a plaque ruptures, clotting cells rush to the site and a clot is formed. Platelets are 'sticky' blood cells that are necessary for helping the blood to clot. Sometimes, however, they too can allow more plaque to develop on an artery wall by causing inflammation.⁴ Clots may completely block a coronary artery and prevent blood from getting to the heart, which can lead to heart attacks or the chest pain of unstable angina.

Each person has more than 30,000 genes—the building blocks of life—that determine what we look like and instruct our bodies how to work.⁵ Each day, scientists are learning more about the genes that can cause certain diseases, including CAD.

One interesting way of doing this is to look at closely related groups of people (such as families) or to look at groups of people who are very similar, such as those who may be isolated from other groups because of geography. One such example is Iceland.

Scientists have been able to discover genes in some of the people of Iceland that appear to nearly double the risk of having a heart attack. One gene seems to prove even more certainly that inflammation of the artery walls makes CAD worse. This gene, called the FLAP gene, increases the inflammation in the wall of the artery, which may increase the risk of having a heart attack or stroke.⁶

The next step for researchers is to find drugs that will help block this gene. Most likely, there are hundreds of genes waiting to be discovered that may help trigger CAD.

Another example is Tangier Island, which is located just off the coast of Virginia. The population of the island is very small—there are only about 700 inhabitants. However, many of the people on the island have a rare genetic disorder called Tangier disease. People with the disease have almost no HDL (the good cholesterol) and are at increased risk for heart attacks. The faulty gene in this disease is ABC1, also known as ABCA1. This gene has been shown to play a role in controlling how fast excess cholesterol is pumped out of certain types of cells.

Fats—the bad and the good

Since you can’t change your genes, one of the ways you can improve your condition and reduce the risk of complications later in life is to keep fat levels in your blood to a minimum. Fats are the main culprits in the making of plaques. Two major kinds of fats make up most of the problem: cholesterol and triglycerides.

Cholesterol

Your body needs cholesterol—it is an important substance in the walls of each cell in the body, it helps make some hormones and vitamin D, and it is part of the bile acids that break down fats in our digestive system.

The liver makes all the cholesterol your body needs for proper functioning, so when you eat too many foods that are high in cholesterol, you're actually getting too much of a necessary thing. Eating large quantities of saturated fats can lead to having more cholesterol in the body than is needed, and much of it tends to stay in the bloodstream. Saturated fats are found primarily in meats (beef, chicken, and pork) and dairy products (such as cheese). Cholesterol travels in the bloodstream on substances called lipoproteins. If your doctor mentions "bad cholesterol" and "good cholesterol" to you, he or she is talking about these lipoproteins. Two main types of lipoproteins carry cholesterol. The difference is how much cholesterol is carried by each one, and how that cholesterol behaves.

Low-density lipoprotein (also called LDL) is what your doctor meant by "bad cholesterol." LDL carries cholesterol to the blood vessels from the liver. LDL is bad because the cholesterol can easily slip off the lipoprotein and stick to an artery wall. Over time, cholesterol from LDL adds to the plaque buildup already in progress. This process narrows the artery and causes less blood and oxygen to reach the heart.

High-density lipoprotein (HDL) is "good cholesterol." HDL is good because it carries cholesterol away from the coronary arteries and other parts of the body back to the liver for removal. The more HDL you have, the less cholesterol is available to attach to artery walls. All this may be a bit confusing but just remember: "LDL is bad—keep it low! HDL is good—keep it high !"

The goals for controlling cholesterol are defined by the National Heart, Lung, and Blood Institute:⁷

Total cholesterol: less than 200 milligrams per deciliter (mg/dL)

LDL: less than 100 mg/dL (for people at very high risk for CAD, 70 mg/dL may be chosen⁸)

HDL: greater than or equal to 40 mg/dL

Learn more about how to manage cholesterol in your diet in Nutrition Matters.

Triglycerides

Triglycerides are another type of fat that can be found in the bloodstream. They are made from the fats and sugars you eat but that your body doesn't use right away. Doctors aren't yet sure to what extent triglycerides contribute to coronary artery disease. But if your doctor has told you that your triglycerides are high, and you have high levels of bad cholesterol and low levels of good cholesterol, your chance of developing heart disease may be high, too. If you're overweight or have diabetes or high blood pressure, your risk may be higher still.⁹

Saturated Fat

Saturated fats typically come from animal fat, although they can be found in vegetable oils such as palm and coconut oil. These fats are solid at room temperature, and are often contained in processed and fast food. Foods such as cheese, cream, butter, and fatty meats also have a lot of saturated fat. Because this kind of fat can cause the body to produce more LDL cholesterol, eating too much of it is unhealthy.

Trans Fats

Trans fats are made when hydrogen is added to liquid (vegetable) oils to make them solid. This changes the chemical structure of the oil and makes it more ‘saturated.’ By adding hydrogen (or ‘hydrogenating’) these oils, food products can last longer at the grocery store. Commercially baked foods such as cookies and crackers often contain trans fats, as do some fried and processed foods and margarines. Trans fats not only raise your levels of bad cholesterol, they can also lower your levels of good cholesterol.

The good news for consumers is that the FDA is planning to require manufacturers to print the levels of trans fatty acids on all food labels.¹⁰ Until then, you can try to reduce your intake of these fats by avoiding products that have hydrogenated oils. Foods that have partially hydrogenated oils or vegetable shortening may contain trans fats.

	Chest pain or discomfort may have causes other than angina. Which of the following should your doctor rule out before diagnosing angina? Click here.

Source

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4. Akbiyik F, Ray DM, Gettings KF, Blumberg N, Francis CW, Phipps RP. Human Bone Marrow Megakaryocytes and Platelets Express PPAR{gamma} and PPAR{gamma} Agonists Blunt Platelet Release of CD40 Ligand and Thromboxanes. Blood. 2004;104:1361-1368: PubMed

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9. Gibbons RJ, Abrams J, Chatterjee K, et al. ACC/AHA 2002 Guideline Update for the Management of Patients with Chronic Stable Angina: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for the Management of Patients with Chronic Stable Angina). 2002. Available at www.acc.org/clinical/guidelines/stable/stable.pdf. Accessed June 24, 2004.

10. American Heart Association. FDA’s New Nutrition Labeling Requirement for Trans Fatty Acids. Available at http://www.americanheart.org/presenter.jhtml?identifier=3013636. Accessed July 20, 2004.