Heart Attack and Acute Coronary Syndrome |
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DescriptionAn in-depth report on the causes, diagnosis, treatment, and prevention of heart attack. |
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Alternative NamesBeta Blockers |
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Risk FactorsAbout 12.6 million Americans currently have heart disease and 1.1 million people are expected to have a serious heart event each year. An estimated 25% of all Americans have one or more risk factors for heart disease. Most risk factors for heart disease are related to lifestyle and environmental factors. 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 US and other industrialized nations. There have also been minimal changes in other risk factors, including smoking, sedentary behavior, and blood pressure control. Some risk factors cannot be changed, including age, gender, and genetics. Nevertheless, their effects can still be modified with healthy lifestyle changes.
Nonmodifiable Risk FactorsAge. About 85% of people who die from heart disease are over the age of 65. Gender. Coronary artery disease and heart attacks are much more common in middle-aged men. Women have, on average, ten to fifteen more years of heart-disease free life than do men, but as women age, they catch up to men. Women, in fact, are more likely to have angina than men are. The American Heart Association reported in 2002 that four million women had angina compared to 2.4 million men. Younger women with heart disease often do not have the same symptoms as their male counterparts and may be less likely to be diagnosed correctly. They are also more likely than men are to die after a heart attack. Evidence suggests that this is because women tend to be older and sicker than men at the time of a first attack. A 2002 study indicated, however, that with early aggressive treatment women with acute coronary syndrome do as well or better than men with the same condition and treatments. Genetic Factors. Genetics are involved in increasing the likelihood of developing important risk factors (e.g., diabetes and high blood pressure). For example, one genetic variant called apolipoprotein E4 (ApoE4) affects cholesterol levels, particularly those associated with heart disease. Ethnicity. Of all major ethnic groups, African American women face the highest risk for death from heart disease, and their rate of heart attacks is increasing. (Mortality rates in men do not differ much by race.) Native American men have a lower risk for heart disease than Caucasian men, and Hispanics have the lowest risk for heart disease of all major American population groups. African Americans face a number of biologic and social dangers to their hearts:
Cholesterol and Other LipidsCholesterol. Cholesterol is a white, powdery substance that is found in all animal cells and in animal-based foods (not in plants). In spite of its bad press, cholesterol is an essential nutrient necessary for many functions. When cholesterol levels rise in the blood, they can have dangerous consequences, depending on the type of cholesterol, particularly low-density lipoprotein (LDL) cholesterol. For example, according to a 2000 study, men with cholesterol levels over 240 mg/dl have a risk that is 2.15 to 3.63 times higher than those whose cholesterol is below 200. A number of studies have now demonstrated that reducing LDL and total cholesterol levels and boosting HDL levels have improved survival and prevented heart attacks. Only 40% of people with high cholesterol levels actually die of heart disease, however, and experts cannot yet define which people are most at risk from high cholesterol levels. Triglycerides. Triglycerides are made up of fatty acid molecules and are the basic chemicals in animal and plant fats. Evidence now suggests that these molecules may be major troublemakers for the heart. Triglycerides appear to interact with HDL cholesterol in such a way that HDL levels fall as triglyceride levels rise. Low HDL is known to be harmful to the heart. The harmful imbalance of high triglycerides with low HDL levels is also associated with obesity (particularly around the abdomen), insulin resistance, and diabetes. Some evidence further suggests that high triglycerides pose other dangers, regardless of cholesterol levels. Triglycerides, for example, may be responsible for blood clots that form and block the arteries. High triglyceride levels are also associated with the inflammatory response--the harmful effect of an overactive immune system that can cause considerable damage to cells and tissues, including the arteries.
Other Lipids. Elevated levels of other fatty molecules (lipids) are also now thought to be important indicators of heart disease risk. Studies are finding an elevated risk for angina and first heart attacks in people with elevated levels of lipoprotein(a), or lp(a). This lipoprotein falls somewhere in density between HDL and LDL and may have some properties that increase the risk for blood clots. Some experts suggest, however, that high levels of lp(a) may merely be markers of late-stage atherosclerosis, not a cause.) [For more information, see the Well-Connected Reports #23, Cholesteroland #43, Heart Healthy Diet.] High Blood PressureHigh blood pressure, or hypertension, has long been a proven cause of coronary artery disease. People in normal health should aim for 139/89 mm Hg or less. Patients with certain health problems should aim lower (e.g., blood pressure in patients with kidney insufficiency, heart failure, or diabetes should be equal to or lower than 130/80 mm Hg).
Obesity and Metabolic SyndromeIn America, obesity is at epidemic levels in all age groups. The effect of obesity on cholesterol levels is complex. Although obesity does not appear to be strongly associated with overall cholesterol levels, among obese individuals triglyceride levels are usually high while HDL (beneficial cholesterol) levels tend to be low, both risk factors for heart disease. Obesity, in any case, has other effects (hypertension, increase in inflammation) that pose major risks to the heart. Obesity is a particularly hazardous when it is one of the components of the metabolic syndrome. This syndrome is diagnosed when three of the following are present: abdominal obesity, low HDL cholesterol, high triglyceride levels, high blood pressure, and insulin resistance. Metabolic syndrome is a pre-diabetic condition that is significantly associated with heart disease and higher mortality rates from all causes. A 2002 study estimated that 24% of the population now has this condition. Obesity is highly linked with type 2 diabetes, in any case. And diabetes itself poses a significant risk for high cholesterol levels and heart disease. [For more information, see the Well-Connected Report #53, Weight Control and Diet.] Sedentary Lifestyle and ExercisePeople who are sedentary are almost twice as likely to suffer heart attacks as are people who exercise regularly. Exercise has a number of effects that benefit the heart and circulation, including improving cholesterol and lipid levels, reducing inflammation in the arteries, assisting weight loss programs, and helping to keep blood vessels flexible and open. Studies continue to show that physical activity and avoiding high-fat foods are the two most successful means of reaching and maintaining heart healthy levels of fitness and weight. Experts have been attempting to define how much exercises is needed to produce heart benefits. In 2002, a well-conducted study on overweight adults confirmed previous research that reported beneficial changes in cholesterol and lipid levels even when people performed low amounts of moderate or high intensity exercise (e.g., walking or jogging 12 miles a week). However, more intense exercise is required to significantly change cholesterol levels, notably increasing HDL (the so-called good cholesterol). Overweight people who have trouble losing pounds can still achieve considerable heart benefits by exercising. Resistance (weight) training has also been associated with heart protection. Exercises that train and strengthen the chest muscles may prove to be very important for patients with angina. Some studies suggest that for the greatest heart protection, it is not the duration of a single exercise session that counts but the total daily amount of energy expended. Therefore, the best way to exercise may be in multiple short bouts of intense exercise, which can be particularly helpful for older people. Important warning note: Sudden strenuous exercise (such as snow shoveling and mowing lawns) puts such people at risk for angina and heart attack. Activities that involve raising the arms above the head may also be risky. Patients with angina should never exercise shortly after eating. People with risk factors for heart disease should seek medical clearance and a detailed exercise prescription. And all people, including healthy individuals, should listen carefully to their bodies for signs of distress as they exercise. [SeeWell-ConnectedReport #29, Exercise.] Diabetes and Insulin ResistanceHeart disease and stroke are the leading causes of death in people with diabetes. People with diabetes are at risk for the following heart-risk conditions, and the more of these conditions they have, the worse the outlook:
Diabetics with heart disease may have a higher risk for silent ischemia, a condition in which people have blocked arteries but do not experience the angina, the chest pain that signals heart disease [For more information, seeWell-Connected Reports #9, Diabetes: Type I or #60, Diabetes: Type II.] Peripheral Artery DiseasePeripheral artery disease (PAD) occurs when atherosclerosis affects the extremities, particularly the feet and legs. In fact, 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.) Although signs of heart disease are detected in only 20% to 40% of patients with PAD after an initial diagnosis, studies suggest that when intense heart-diagnostics tests are performed, such as angiography or thallium stress tests, co-existing heart disease is detected in up to 90% of all PAD patients. [For more information, seeWell-Connected Report #102 Peripheral Artery Disease.] SmokingSmokers in their thirties and forties have a heart-attack rate that is five times higher than their nonsmoking peers. Cigarette smoking may be directly responsible for at least 20% of all deaths from heart disease, or about 120,000 deaths annually. Smoking cigars may increase the risk of early death from heart disease, although evidence is much stronger for cigarette smoking. Although heavy cigarette smokers are at greatest risk, a 2002 study suggested that people who smoke as few as three standard brand cigarettes a day are at higher risk for blood vessel abnormalities that endanger the heart. Regular exposure to passive smoke is now estimated to increase the risk of heart disease in the nonsmoker by between 25% and 91%, causing more than 30,000 deaths each year [For more information, see the Well-Connected Report #41 Smoking.] Eating HabitsEating habits can be protective or dangerous to the heart. Although the best diet is not clear for each individual, avoiding saturated fats and trans-fatty acids is recommended for everyone.
Stress and Psychologic FactorsStress. The effects of mental stress on heart disease are controversial. Stress can certainly influence the activity of the heart when it activates the sympathetic nervous system (the automatic part of the nervous system that affects many organs, including the heart). This effect may support the association between acute stress and a higher risk for serious cardiac events, such as heart rhythm abnormalities and heart attacks, in people with heart disease. Nevertheless, not all studies report strong evidence that stress has any effect on the heart, particularly in people without any history of heart disease. [SeeWell-ConnectedReport #31, Stress.] Depression. Depression increases the severity of heart attack and may even impair a patient's response to medication for heart disease. Although people with heart disease may certainly become depressed, this does not explain entirely the link between the two problems. The data are now suggesting that depression itself may be a true risk factor for heart disease as well as its increased severity. A number of studies have suggested that depression has biologic effects on the heart, including blood clotting and heart rate. A study in 2001, for example, reported an association between depression and a greater risk for death from heart problems even in people without a history of heart disease. A 2002 study reported a higher risk for heart failure in women--although not in men--with depression. The more severe the depression, the more dangerous to the health, although even mild depression, including feelings of hopelessness, experienced over many years, may harm the heart, even in people with no early signs of heart disease. [SeeWell-ConnectedReport #8, Depression.] AlcoholBenefits of Moderate Drinking. A number of studies have found heart protection from moderate intake alcohol (defined as one or two glasses a day). The benefits reported have been higher HDL levels, blood clot prevention, and anti-inflammatory properties. Although red wine is most often cited for healthful properties, any type of alcoholic beverage appears to have similar benefit. Adverse Effects of Heavy Drinking on the Heart. It should be strongly noted that heavy drinking harms the heart. And, in fact, cardiovascular disease is the leading cause of death in alcoholics. Evidence suggests that people who consume more than three drinks a day have abnormal blood clotting factors. Heavy alcohol consumption can raise blood pressure and, particularly binge drinking, may also increase the risk for hemorrhagic stroke (caused by bleeding in the brain). Large doses of alcohol can trigger irregular heartbeats, which can be dangerous in people with existing heart disease. Note: Alcohol increases the risk for breast cancer in women. Pregnant women and people who can't drink moderately should not drink at all. Emerging or Possible Risk Factors for Heart DiseaseHomocysteine and Vitamin B Deficiencies. Deficiencies in the B vitamins folate (known also as folic acid) and B12 have been associated with a higher risk for heart disease in some (but not all) studies. Such deficiencies produce elevated blood levels of homocysteine, an amino acid that has been associated with a higher risk for heart disease, stroke, and heart failure. Some studies in 2002 suggest that any risk posed by homocysteine or benefits from folic acid for heart disease are at most modest. One study, however, reported lower failure rates after angioplasty in patients who took folic acid and vitamins B12 and B6. And a major 2002 study suggested that lowering homocysteine levels with folic acid would reduce the risk for heart disease by 16% and stroke by 24%. More evidence is needed to determine whether homocysteine plays a causal role in cardiovascular disease and whether the B vitamins are protective. Folate improves blood flow through the arteries, which may be important for the heart, regardless of affect its on homocysteine. C-Reactive Protein. C-reactive protein is a product of the inflammatory process and evidence increasingly supports the idea that high levels strongly predict future heart disease. Some studies suggest, in fact, that measuring this protein may be as useful for determining future risk for heart disease as measuring LDL cholesterol levels. 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 More evidence is needed to determine the benefits of measuring C-reactive protein before it gains acceptance as a routine screening tool. C. pneumoniae and Other Infectious Agents. Some microorganisms and viruses have been under suspicion for triggering the inflammation and damage in the arteries that contributes 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. In some studies, evidence of previous infection has been associated with a higher risk for heart events. 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. (H. pylori, the bacteria that causes peptic ulcers, has also been studied for heart effects, but evidence is very weak on any link.) Periodontal Disease. A number of studies now strongly supports an association between periodontal disease and cardiovascular disorders. According to a 2003 major analysis, periodontal (gum) disease is associated with a 20% higher risk for ischemic stroke and heart disease. (The added risk may be even higher in adults under 65.) Recent evidence is pointing to the inflammatory response as the common element. Anemia. Anemia has adverse effects on the heart and increases the severity of cardiac conditions, including heart failure and heart attacks. And, in fact, blood transfusions after a heart attack improve survival rates in elderly patients who are anemic. A 2002 study further suggested that anemia might even be a risk factor for heart disease itself. Iron Overload. An inherited disease called hemochromatosis, in which the intestinal tract absorbs too much iron from food, has been associated with atherosclerosis and heart attack. About 10% of Caucasians carry the gene. There is no strong evidence that excess iron levels in people without hemochromatosis can contribute to heart disease. 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. It has been strongly associated with high blood pressure and obesity, but is also associated with heart disease and heart attacks, regardless of these risk factors. Some evidence suggests that obstructive apneas cause an increase in stiffness and inflammation in the arteries. Conditions Associated with Heart DiseaseSome inborn or natural conditions are not risk factors themselves but have been associated with a higher incidence of heart disease or its consequences: Factors Before Birth and In Infancy. Low weight at birth and in the womb has been associated with later heart disease in a few studies. Some studies suggest, however, that this may just reflect poor nutrition in the mother, which appears to affect life-long risk. A 2000 British study reinforced the idea that pre-birth or other early events have little significant effect on heart disease risk in later life. Seasonal Differences. More deaths from heart disease occur in December and January and fewest in the summertime. Although lower temperatures and snow shoveling may play a role in some cases, more winter deaths have been reported even in warm regions. Holiday stress or fewer daylight hours have been suggested as other reasons for these higher winter rates. Physical Characteristics. Male pattern baldness, hair in the ear canals, and creased earlobes are associated with a higher risk for heart disease in white males. (Interestingly, in African American men, of these factors, only creased earlobes were associated with a higher risk in one study.) Air Pollution. A 2000 study suggested that air pollution is linked to a higher risk of death from heart disease as well as lung disease and all other causes. |
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