Risk Factors (Genetics & Inherited Conditions)
Many interrelated risk factors contribute to CHD, with lipoprotein levels, oxidation, inflammation, and thrombosis playing central roles. Lipoproteins transport triglycerides and cholesterol through the blood; their concentrations are determined by diet, exercise, and heredity. The hereditary condition most strongly associated with CHD is familial hypercholesterolemia. Other factors affecting CHD risk (each with its own genetic component) include abdominal fat, diabetes, emotional stress, high blood pressure, hormone treatment after menopause, chronic kidney disease, metabolic syndrome, old age, alcohol abuse, and tobacco smoke. For genetic and environmental reasons, African Americans tend to be at higher risk for CHD than Caucasians, whereas Asians and Hispanics tend to be at lower risk. Males are at higher risk than females, but after menopause the risk evens out.
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Etiology and Genetics (Genetics & Inherited Conditions)
CHD is typically caused by a buildup of fatty plaques in one or more large coronary arteries, a process that often begins in childhood. Although the initiating events are not well understood, it is thought that plaque development occurs at sites of “damage” to the endothelium layer of cells lining the interior of the artery. These sites accumulate low-density lipoprotein particles (LDL cholesterol or LDL-C, often referred to as “bad” cholesterol). The oxidation of these particles incites an inflammatory response. As part of this response, macrophages engulf the oxidized LDL-C but end up being a major part of the problem when they consume too many particles and become foam cells. These cells and others, along with necrotic debris, turn into a fatty streak that triggers plan B: Seal off the area. This strategy is accomplished by creating a fibrous cap over the fat deposit and slowly calcifying the plaque from the bottom up, keeping it separate from the layer of smooth muscle cells that contract and expand the artery. This arrangement works well as long as the cap does not fracture, which it unfortunately does occasionally thanks to blood pressure and more attempts by the inflammatory system to clean things up.
A cracked plaque leaks debris into the artery that immediately triggers thrombosis (clotting). A clot that is not fully occlusive gets degraded but leaves a larger fibrous cap. Consequently, repeated...
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Symptoms (Genetics & Inherited Conditions)
The development of atherosclerosis in coronary arteries has no symptoms. It is only in the later stages, when blood flow to the heart becomes impaired, that problems manifest themselves clinically. The signs are most noticeable during exercise or exertion: unusual fatigue, lightheadedness, palpitations, and a feeling of pressure on the chest. Other forms of physical stress such as anger, eating a heavy meal, or cold exposure can also trigger symptoms. Examination by a physician should be scheduled as soon as possible; damage done by CHD can soon lead to arrhythmia and heart failure (inability to pump sufficient blood). Symptoms of an impending heart attack are similar to those above but persist more than five minutes, even in the absence of exertion. They include nausea, heartburn, breathlessness, cold sweats, and nonspecific pain, pressure, or discomfort in the chest (which may radiate to the shoulders, upper back, neck, jaw, or arms). For women, it has been suggested that these signs are frequently more subtle, oftentimes with no chest pain (only discomfort). If a heart attack is suspected, then the victim should call for an ambulance immediately and chew an aspirin. Pain at an exact spot or chest pain related to breathing is typically not symptomatic of heart attack.
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Screening and Diagnosis (Genetics & Inherited Conditions)
CHD is the leading cause of death in developed countries for both men and women; the number of deaths attributable to CHD in the United States averages almost 1,400 per day (about 500,000 per year). Screening for CHD risk should begin early in adulthood. This is accomplished by assessing blood pressure, family history, lifestyle, and biomarkers in the blood. The commonly used blood measurements are the fasting levels of glucose, total cholesterol, LDL-C (greater than 130 mg/dL = high risk), HDL-C (less than 40 mg/dL = high risk), triglycerides, homocysteine, and C-reactive protein (CRP), a marker of inflammation. Genetic tests are also becoming available for assessing CHD risk but their added value has not been established; the 9p21 variant noted appears to have a small amount of predictive value independent of standard blood tests.
A variety of tests are used to diagnose advanced atherosclerosis and CHD. The gold standard is angiography: a catheter is threaded through an artery that releases a dye for X-ray viewing of the blood flow to the heart. Other methods of visualizing heart and vascular function include computed tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), radionuclide imaging, and ultrasound imaging (Doppler and echocardiogram). A different kind of test, the electrocardiogram, measures abnormalities in the electrical impulses regulating the heart; this test and others...
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Treatment and Therapy (Genetics & Inherited Conditions)
Intervention usually begins with lifestyle changes—stopping smoking, managing stress, exercising more, eating less. Dietary recommendations also include taking in a greater proportion of calories from a variety of fruits, vegetables, beans (garbanzo, lima), whole grains (brown rice, oats, whole wheat), lean meats (chicken), oily fish (salmon, sardine, trout, tuna), tree nuts (almonds, pecans, walnuts), nonhydrogenated oils (olive, canola, sunflower), and low-fat dairy. These guidelines are meant to increase the intake of complex carbohydrates, soluble fiber, polyphenolic flavonoids, plant sterols, and omega-3 fatty acids while decreasing the intake of simple sugars, cholesterol, saturated fats, and trans fats. With the exception of omega-3 fatty acids and niacin, taking dietary supplements (vitamins B6, B12, C, and E and folic acid) has not proved to be effective. Niacin supplementation at high doses is beneficial for boosting HDL-C, although blood testing should be done for potential liver damage. Limited alcohol intake and moderately intense aerobic exercise (not necessarily at the same time) also improve HDL-C and provide other vascular benefits (limited alcohol means one drink per day for women, up to two for men). Reducing sodium intake relative to potassium intake helps lower blood pressure.
When diet and lifestyle changes are not sufficient, various drug options are available. High levels of bad cholesterol are...
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Prevention and Outcomes (Genetics & Inherited Conditions)
Preventing CHD requires all the lifestyle changes noted above. Any reduction in LDL-C or increase in HDL-C is also helpful regardless of baseline levels. Risk factors such as blood pressure, LDL-C, HDL-C, triglycerides, blood glucose, homocysteine, sodium, potassium, and C-reactive protein should be monitored with blood tests and regular checkups. Simple hygiene measures such as habitual brushing and flossing of teeth can also reduce inflammation (gingivitis) and CHD risk. Such lifestyle changes are critically important because once atheromatous plaques reach the fibrous stage, they are essentially permanent. A heart-healthy lifestyle is also important for good health regardless of genetic risk for CHD. Genetic testing is largely beneficial only for those with a family history of early-onset CHD so that treatment is initiated early and aggressively. For others, testing for one or a few risk alleles is fraught with uncertainty given the huge number of genetic and environmental interactions affecting penetrance.
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Further Reading (Genetics & Inherited Conditions)
Crowley, Leonard V. An Introduction to Human Disease, Pathology and Pathophysiology Correlations. 7th ed. Boston: Jones & Bartlett, 2006. Contains a chapter devoted to the cardiovascular system and a section specific to coronary heart disease that is easy to understand and well illustrated.
Marin-Garcia, Jose, with Michael J. Goldenthal and Gordon W. Moe. Aging and the Heart: a Post Genomic View. New York: Springer, 2008. Thorough and comprehensive, covers all aspects of cardiovascular aging and diseases, including genetics and therapies. Indexed, well referenced, and available electronically.
Mittal, Satish. Coronary Heart Disease in Clinical Practice. London: Springer, 2005. Covers all aspects of CHD (including genetics) from plaque development to thrombosis to acute heart failure. Indexed, well referenced, and available electronically.
Wright, Alan, and Nicholas Hastie, eds. Genes and Common Diseases, Genetics in Modern Medicine. Cambridge, England: Cambridge University Press, 2007. Contains a chapter on the genetics of coronary heart disease written by experts in the field. Includes a discussion of rodent models.
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Web Sites of Interest (Genetics & Inherited Conditions)
American Heart Association. http://www.americanheart.org/presenter .jhtml?identifier=1200000
British Heart Foundation. http://www.bhf.org.uk
Heart and Stroke Foundation of Canada. http://ww2.heartandstroke.ca/splash
U.S. National Library of Medicine, Genetics Home Reference. http://ghr.nlm.nih.gov/condition = hypercholesterolemia
WebMD: Coronary Artery Arteriosclerosis. http://medscapecrm.net/article/153647-overview
Wrong Diagnosis: Coronary Artery Disease. http://www.wrongdiagnosis.com/c/coronary _heart_disease/book-diseases-7a.htm
Wikipedia: Atheroma, Atherosclerosis, Coronary Artery Disease, High-Density Lipoprotein, Low-Density Lipoprotein. http://en.wikipedia.org/wiki
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Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
The heart is a fist-sized organ located in the lower left quarter of the chest. It consists of four chambers: the right and left atria on top and the right and left ventricles at the bottom. The chambers are enclosed in three layers of tissue: the outer layer (epicardium), the middle layer (myocardium), and the inner layer (endocardium). Surrounding the entire organ is the pericardium, a thin layer of tissue that forms a protective covering for the heart. The heart also contains various nodes that transmit electrochemical signals, causing heart muscle tissue to contract and relax in the pumping action that carries blood to organs and cells throughout the body.
Signals from the brain cause the heart to contract rhythmically in a sequence of motions that move the blood from the right atrium down through the tricuspid valve into the right ventricle. From here, blood is pushed through the pulmonary valve into the lungs, where it fulfills one of its major functions: to pick up oxygen in exchange for carbon dioxide. From the lungs, the blood is pumped back into the heart, entering the left atrium from which it is pumped down through the mitral valve into the left ventricle. Blood is then pushed through the aortic valve into the main artery of the body, the aorta, from which it starts its journey to the organs and cells. As it passes through the arteries of the gastrointestinal system, the blood picks up nutrients which, along...
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Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
The main tools for diagnosing heart disease are the stethoscope, the electrocardiograph (ECG), and the X ray. With the stethoscope the doctor listens to heart sounds, which provide information about many heart functions such as rhythm and the status of the valves. The doctor can determine whether the heart is functioning normally in pumping blood from one chamber into the other, into the lungs, and into the aorta. The ECG gives the doctor a graph representation of heart function. Twelve to fifteen electrodes are placed on various parts of the body, including the head, chest, legs, and arms. The activities of the heart are printed on a strip of paper as waves or tracings. The doctor analyzes the printout for evidence of heart abnormalities, changes in heart function, signs of a heart attack, or other problems. Generally, the electrocardiographic examination is conducted with the patient at rest. In some situations, however, the doctor wishes to view heart action during physical stress. In this case, the electrodes are attached to the patient and the patient is required to exercise on a treadmill or stationary bicycle. The physician can see what changes in heart function occur when the cardiac workload is increased. The X ray gives the doctor a visual picture of the heart. Any enlargements or abnormalities can be seen, as well as the status of the aorta, pulmonary arteries, and other structures.
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Heart disease became a major killer in the United States in the twentieth century. In the early decades, the best that the medical community could do was to treat symptoms. Since then, the emphasis has shifted to prevention. Hundreds of investigative studies have been undertaken to determine the causes of the most prevalent heart dysfunction, coronary artery disease. Many of these studies have involved tens of thousands of subjects, and they point to a general consensus that coronary artery disease is a multifactorial disorder, the primary elements of which are cholesterol and other fatty substances circulating in the bloodstream, smoking, diabetes, high blood pressure, stress, and obesity.
The reasons that mortality from heart disease is declining include improved medications and treatment modalities, and much credit has to be given to the success of preventive measures. Millions of Americans have stopped smoking and have begun watching their diets. Entire industries are devoted to helping Americans eat more intelligently. While fast-food outlets continue to offer high-fat standards, such as hot dogs and hamburgers, they have also added salads and leaner selections.
Perhaps most important, medical and sociological authorities have turned their attention to children. Because advanced atherosclerosis has been detected in young men and women, cholesterol-watching has become a major preoccupation with parents...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
American Heart Association. http://www.american heart.org. Site provides comprehensive information on heart disease and conditions, healthy lifestyles, and resources, and provides interactive health tools.
Baum, Seth J. The Total Guide to a Healthy Heart: Integrative Strategies for Preventing and Reversing Heart Disease. New York: Kensington, 2000. This book brings together the practices of both conventional and alternative approaches to reversing heart disease and maintaining heart health. Offers great insight into why the integrative approach to maintaining a healthy heart will be the medicine of the new millennium.
Gersh, Bernard J., ed. The Mayo Clinic Heart Book. 2d ed. New York: William Morrow, 2000. One of the most respected texts for laypeople on heart disease. Covers all aspects of anatomy, physiology, diagnosis, treatment, and prevention.
Goldberg, Nieca. Women Are Not Small Men: Life-Saving Strategies for Preventing and Healing Heart Disease in Women. New York: Random House, 2003. Written by the founder and chief of the Women’s Heart Program at New York’s Lenox Hill Hospital, details the way in which women experience heart disease and recovery in fundamentally different ways than men do. Physiology, symptoms, and treatment and medications are scrutinized.
Kramer, Gerri Freid, and Shari Mauer. Parent’s Guide to Children’s Congenital Heart Defects:...
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Heart Disease (Encyclopedia of Alternative Medicine)
Heart disease is the narrowing or blockage of the arteries and vessels that provide oxygen and nutrient-rich
blood to the heart. It is caused by atherosclerosis, an accumulation of fatty materials on the inner linings of arteries that restricts blood flow. When the blood flow to the heart is completely cut off, the result is a heart attack because the heart is starved of oxygen.
Heart disease, also called coronary heart disease or coronary artery disease, is the leading cause of death for both men and women in the United States. According to the American Heart Association, deaths from coronary artery disease have declined somewhat since about 1990, but more than 40,000 people still died from the disease in 2000. About 13 million Americans have active symptoms of coronary artery disease.
Heart disease occurs when the coronary arteries become partially...
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