An in-depth report on the causes, diagnosis, treatment, and prevention of coronary artery disease (CAD).
Angina; Atherosclerosis; Heart disease
Heart disease is the leading cause of death in the United States. Over the past decades, heart disease rates declined in both men and women as they quit smoking and improved dietary habits. This rate, however, has stabilized in recent years, most likely because of the dramatic increase in obesity in the U.S. and other industrialized nations.
The risks for coronary artery disease increase with age. About 85% of people who die from heart disease are over the age of 65.
Men have a greater risk for coronary artery disease and are more likely to have heart attacks earlier in life than women. Womenâ ' s risk for heart disease increases after menopause, and they are more likely to have angina than men.
Certain genetic factors increase the likelihood of developing important risk factors, such as diabetes and high blood pressure. For example, one genetic variant called apolipoprotein E4 (ApoE4) affects cholesterol levels, particularly those associated with heart disease.
Heart disease tends to run in families. People whose parents or siblings developed heart disease at a younger age are more likely to develop it themselves.
African-Americans have the highest risk of heart disease, in part due to their high rates of severe high blood pressure, as well as diabetes and obesity.
Smoking. Smoking is the most important risk factor for heart disease. Smoking can cause elevated blood pressure, worsen lipids, and make platelets very sticky, raising the risk of clots. Cigarette smoking may be directly responsible for at least 20% of all deaths from heart disease. Although heavy cigarette smokers are at greatest risk, people who smoke as few as three cigarettes a day are at higher risk for blood vessel abnormalities that endanger the heart. Regular exposure to passive smoke also increases the risk of heart disease in nonsmokers. [For more information, see In-Depth Report #41: Smoking.]
Alcohol. Moderate alcohol consumption (one or two drinks a day; 5 ounces wine, 12 ounces beer, or 1.5 ounces hard liquor is one drink) can help boost HDL âgoodâ cholesterol levels. Alcohol may also prevent blood clots and inflammation. By contrast, heavy drinking harms the heart. In fact, heart disease is the leading cause of death in alcoholics.
Diet. Diet plays an important role in the health of the heart, especially in controlling dietary sources of cholesterol and restricting salt intake that contributes to high blood pressure. [For more information, see In-Depth Report#43: Heart-healthy diet.]
Physical Inactivity. Exercise has a number of effects that benefit the heart and circulation, including improving cholesterol and lipid levels and maintaining weight control. People who are sedentary are almost twice as likely to suffer heart attacks as are people who exercise regularly.
Obesity and Metabolic Syndrome. Excess body fat, especially around the waist, can increase the risk for heart disease. Obesity also increases the risk for other conditions (high blood pressure, diabetes) that are associated with heart disease. Obesity is particularly hazardous when it is part of the metabolic syndrome, a pre-diabetic condition that is significantly associated with heart disease. This syndrome is diagnosed when three of the following are present:
[For more information, see In-Depth Report #53: Weight control and diet.]
Unhealthy Cholesterol and Lipid Levels. Low-density lipoprotein (LDL) cholesterol is the "bad" cholesterol responsible for many heart problems. Triglycerides are another type of lipid (fat molecule) that can be bad for the heart. High-density lipoprotein (HDL) cholesterol is the "good" cholesterol that helps protect against heart disease. Doctors test for a "total cholesterol" profile that includes measurements for LDL, HDL, and triglycerides. The ratio of these lipids can affect heart disease risk. [For more information, including cholesterol goals, see In-Depth Report #23: Cholesterol.]
High Blood Pressure. High blood pressure, or hypertension, has long been a proven cause of coronary artery disease. A normal blood pressure reading is 120/80 mm Hg or lower. High blood pressure is generally considered to be a blood pressure reading greater than or equal to 140 mm Hg (systolic) or greater than or equal to 90 mm Hg (diastolic). Blood pressure readings in the prehypertension category (120 - 139 systolic or 80 - 89 diastolic) indicate an increased risk for developing hypertension. [For more information, see In-Depth Report #14: High blood pressure.]
Diabetes. Diabetes, especially for people whose blood sugar levels are not well controlled, significantly increases the risk of developing heart disease. In fact, heart disease and stroke are the leading causes of death in people with diabetes. People with diabetes are also at risk for high blood pressure and unhealthy cholesterol levels, blood clotting problems, and impaired nerve function, all of which can damage the heart. [For more information, see In-Depth Report #9: Diabetes - type 1 or In-Depth Report #60: Diabetes - type 2.]
Peripheral Artery Disease. Peripheral artery disease (PAD) occurs when atherosclerosis affects the extremities, particularly the feet and legs. The major risk factors for heart disease and stroke are also the most important risk factors for PAD. (The combination of such conditions with PAD also produces more severe forms of heart or circulatory disease.) Even though signs of heart disease are often not evident in the majority of patients with PAD, most of these patients also have coronary artery disease present. [For more information, see In-Depth Report #102: Peripheral artery disease. ]
Depression. Although people with heart disease may become depressed, this does not explain entirely the link between the two problems. Data suggest that depression itself may be a risk factor for heart disease as well as its increased severity. A number of studies indicate that depression has biologic effects on the heart, including blood clotting and heart rate. [For more information, see In-Depth Report #8: Depression.]
Homocysteine and Vitamin B Deficiencies. Deficiencies in the B vitamins folate (known also as folic acid), B6, and B12 have been associated with a higher risk for heart disease in some studies. Such deficiencies produce higher blood levels of homocysteine, an amino acid that has been associated with a higher risk for heart disease, stroke, and heart failure.
However, while B vitamin supplements do help lower homocysteine levels, they appear to have no effect on heart disease outcomes, including preventing heart attack or stroke. Research indicates that homocysteine may be a marker for heart disease rather than a cause of it.
C-Reactive Protein. C-reactive protein (CRP) is a product of the inflammatory process. Evidence increasingly suggests that high levels may predict future heart disease. It is not known if the protein plays any causal role or whether it is simply a marker for other factors in the disease process.
C. pneumoniae and Other Infectious Organisms. Some microorganisms and viruses have been under suspicion for triggering the inflammation and damage in the arteries that contribute to heart disease. The strongest evidence to date supports a possible role from Chlamydia (C.) pneumoniae (a non-bacterial organism that causes mild pneumonia in young adults). C. pneumoniae has been detected in plaques in the arteries of patients with heart disease. However, treatment with appropriate antibiotics is not found to reduce the risk of future heart problems for patients infected with this organism.
Other studies also suggest that cytomegalovirus (CMV), a common virus, may have similar effects. Many people, however, have been infected with these organisms, and no clear association has been found with any of these infections.
Sleep Apnea. Obstructive sleep apnea is a condition in which tissues in the upper throat collapse at intervals during sleep, thereby blocking the passage of air. About a third of patients with coronary artery disease also have obstructive sleep apnea. Patients with severe, untreated apnea have been found to have an increased incidence of stroke and cardiac events (such as heart attack). However, there is no evidence to date that identifies obstructive sleep apnea as an independent cause of cardiac events or stroke.
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