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Heart attack and acute coronary syndrome

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of heart attack.

Alternative Names

Acute coronary syndrome; Myocardial infarction

Risk Factors

An estimated 25% of all Americans have one or more risk factors for heart disease, increasing their risk for heart attack. Most risk factors for heart disease are related to lifestyle. Some risk factors, (such as age, gender, and ethnicity) cannot be changed. Nevertheless, overall risks can be reduced with healthy lifestyle changes. [For more information on heart disease, see In-Depth Report #3: Coronary artery disease.]

Guidelines for Preventing Heart Disease and Stroke The American Heart Association's guidelines for preventing heart disease recommend: Improve Cholesterol. People with at least two risk factors and a 10-year risk for heart disease or stroke of more than 20% should aim for LDL levels of less than 100 mg/dl. Statins are now used in more cases. Keep Blood Pressure Low. People in normal health should have a blood pressure reading of 120/80 mm Hg or less. According to new guidelines, blood pressure readings of 120/80 are considered normal, readings of 140/90 or higher indicate hypertension, and readings in between the two are called pre-hypertension. Patients with diabetes or chronic kidney disease should maintain blood pressure readings of 130/80 mm Hg or less, while others should be no higher than 140/90 mm Hg. Exercise. Everyone in normal health should engage in at least moderate physical activity for a minimum of 30 minutes on most -- if not all -- days of the week. Healthy Diet. Everyone should aim for a diet that contains a healthy balance of fruits, vegetables, grains, fish, nuts, legumes, poultry, lean meat, and low-fat dairy items. Avoid saturated fats and trans-fatty acids. Quit Smoking. Also avoid exposure to second-hand smoke. Maintain Weight. People should aim for a BMI index of 18.5 to 24.9. Take Aspirin. People at high risk for heart disease should take a low-dose aspirin every day, unless they have medical reasons to avoid aspirin. Control Diabetes. People with diabetes should aim for fast blood glucose levels of less than 110 mg/dl and hemoglobin A1C of less than 7%. Control Atrial Fibrillation. People with atrial fibrillation should use anticoagulants to reduce the risk for blood clots. Managing Acute Coronary Syndrome The approach for managing acute coronary syndrome involves lifestyle changes and medications. Experts have come up with a mnemonic device (ABCDE) for remembering the factors that are fundamental for management of acute coronary syndrome: A. Antiplatelets, anticoagulants, and ACE inhibitors B. Blood pressure and beta-blockers C. Cholesterol-lowering drugs (typically statins) and cigarettes (stopping) D. Diet and diabetes control E. Exercise and education

Nonmodifiable Risk Factors

Age. 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, 10 to 15 more years of heart disease-free life than do men, but as women age, they catch up to men. Women are more likely to have angina than men are. 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.

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.

Cholesterol and Other Lipids

Cholesterol. 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. However, when certain cholesterol levels rise in the blood, they can have dangerous consequences, depending on the type of cholesterol.

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, see In-Depth Report #23: Cholesterol.]

Cholesterol Goals. In 2004, the National Cholesterol Education Program updated its clinical practice guidelines. The new recommendations set lower treatment goals for LDL levels based on a patient's risk factors for heart disease.

These risk factors include:

• Having a first-degree female relative diagnosed with heart disease before age 65 or a first-degree male relative diagnosed before age 55
• Being male and over age 45 or female and over age 55
• Cigarette smoking
• Diabetes
• High blood pressure
• Metabolic syndrome (risk factors associated with obesity such as low HDL levels and high triglycerides)

Having two or more of these risk factors indicates a greater than 20% chance of having a heart attack within 10 years.

LDL Goals
Risk Level	Goal (d/L)	Optimal Goal (d/L)
Very High Risk	70	70
High Risk	100	70
Moderate Risk	130	100
Low Risk	160	130

LDL cholesterol, together with other risk factors for heart disease, is the best determinant for whether cholesterol therapy is needed and whether it is working properly. In particular, the new guidelines emphasize lower LDL levels and earlier treatment for people with coronary artery disease, or other forms of atherosclerosis, and diabetes.

Cholesterol Goals
Total Cholesterol Goals	LDL Goals	HDL Goals	Triglyceride Goals
Less than 200 mg/dL is desirable. Between 200 and 239 is borderline. Over 240 is high.	70 mg/dL or less is the new goal for very high-risk patients (recent heart attack; current active or unstable cardiovascular or cerebrovascular disease; or two multiple risk factors as defined above.) Below 100 mg/dl is optimal for everyone. It should be the goal for high-risk people including those with existing heart disease, diabetes, or two or more risk factors for heart disease; 70 mg/dL is an optimal goal for these individuals. 130 mg/dl or below for people with two or more risk factors; 100 mg/dL is the optimal goal. 160 mg/dl or less for people at less risk (one or zero risk factors); 130 mg/dL is an optimal goal. Anything over 160 is high, with levels over 190 being very high. LDL levels over 190 require medication even with no other cardiac risk factors present.	Levels above 40 mg/dL are desirable; levels above 60 mg/dL are optimal.	Below 150 mg/dL is normal. 150-199 is borderline high. 200-499 is high. Over 500 is very high.
*Risk factors for heart disease include a family history of early heart problems before age 55 for men, before age 65 for women), smoking, high blood pressure, diabetes, being older (over 45 for men and 55 for women), and having HDL levels below 35 mg/dl. People with two or more of these risk factors may have a 10-year risk of heart attack that exceeds 20%, and may therefore need to aim for LDL levels of 100 mg/dL or below.

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.

High Blood Pressure

High blood pressure, or hypertension, has long been a proven cause of coronary artery disease. Blood pressure is categorized as normal, prehypertensive, and hypertensive (which is further divided as Stage 1 or 2 according to severity). 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. [See Table Blood Pressure Ranges.]

A normal blood pressure reading is 120/80 mm Hg or lower. Most people with high blood pressure should aim for a goal of below 140/90 mm Hg. Patients with certain health problems should aim lower (blood pressure in patients with kidney disease, heart failure, or diabetes should be equal to or lower than 130/80 mm Hg.) [For more information, see In-Depth Report #14: High blood pressure.]

Blood Pressure Ranges
Blood Pressure Category	Ranges for Most Adults (systolic/diastolic)
Normal Blood Pressure (systolic/diastolic)	Systolic below 120 mm Hg Diastolic below 80 mm Hg
Prehypertension (Formerly Classified as Normal to High-Normal Blood Pressure)	Systolic 120 to 139 mm Hg Diastolic 80 to 89 mm Hg (NOTE: 139/89 or below should be the minimum goal for everyone. People with diabetes or chronic kidney disease should strive for 130/80 or less . )
Mild Hypertension (Stage 1)	Systolic 140 to 159 mm Hg Diastolic 90 to 99 mm Hg
Moderate to Severe Hypertension (Stage 2)	Systolic over 160 mm Hg and/or Diastolic over 100 mm Hg
Note: If one of the measurements is in a higher category than the other, the higher measurement is usually used to determine the stage. For example, if systolic pressure is 165 (Stage 2) and diastolic is 92 (Stage 1), the patient would still be diagnosed with Stage 2 hypertension. It should be strongly noted that a high systolic pressure should be a major focus of concern in most adults.

Obesity and Metabolic Syndrome

American 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 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 In-Depth Report #53: Weight control and diet.]

Sedentary Lifestyle and Exercise

People who are sedentary are almost twice as likely to suffer heart attacks as are people who exercise regularly. Exercise has several 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 exercise 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 (walking or jogging 12 miles a week). However, more intense exercise is required to significantly change cholesterol levels, notably by 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.

Sudden strenuous exercise (such as snow shoveling and mowing lawns) can put 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. [See In-Depth Report #29: Exercise.]

Diabetes and Insulin Resistance

Heart 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:

• High blood pressure (hypertension) -- up to 75% of cardiovascular problems in people with diabetes may be due to hypertension.
• Very unhealthy cholesterol and lipid balances (high triglyceride levels and lower high density lipoprotein)
• Blood clotting problems
• Impaired nerve function (neuropathy), which can also damage the heart. In fact, some experts estimate that the mortality rates from neuropathy-related heart conditions ranges from 15 - 53%

Patients with both diabetes and 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, see In-Depth Reports #9: Diabetes - type 1 or #60: Diabetes - type 2.]

Smoking

Smokers in their 30s and 40s 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 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.]

Eating Habits

Eating habits can either protect or hurt the heart. Experts generally agree on the following heart-smart recommendations:

• Choose fiber-rich food (whole grains, legumes, nuts) as the main source of carbohydrates, along with a high intake of fresh fruits and vegetables.
• Avoid saturated fats (found mostly in animal products) and trans fatty acids (found in hydrogenated fats and many commercial products and fast foods). Choose unsaturated fats, particularly omega-3 fatty acids (found in vegetable and fish oils).
• In selecting proteins, choose soy, legumes, poultry, and fish over meat. Fat free and low fat dairy products (skimmed milk, yogurt) are also healthy choices.
• Controlling weight, quitting smoking, and exercising are essential companions of any diet program.

After starting any heart healthy diet, it generally takes an average of 3 to 6 months before any noticeable reduction in cholesterol occurs, although some people have reported better levels in as few as 4 weeks. An intensive program may be necessary to achieve significant improvements in cholesterol levels and to reduce other heart risk factors. [For more information, see In-Depth Report #43: Heart-healthy diet.]

Stress and Psychologic Factors

Stress. The effects of mental stress on heart disease are controversial. Stress can affect the heart when it activates the sympathetic nervous system (the automatic part of the nervous system that affects many organs, including the heart). Some studies suggest an 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. However, not all studies report strong evidence that stress has any effect on the heart, particularly in people without any history of heart disease. [See In-Depth Report #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 now suggest that depression itself may be a true risk factor for heart disease as well as its increased severity. Several 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. [See In-Depth Report #8: Depression.]

Alcohol

Benefits of Moderate Drinking. Several studies have found heart protection from moderate intake of alcohol (one or two glasses a day). Moderate alcohol consumption can help boost HDL levels. Alcohol may also prevent blood clots and inflammation. 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. By contrast, heavy drinking harms the heart; heart 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 binge drinking may 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.

Pregnant women and people who can't drink moderately should not drink at all.

Other Risk Factors

Anemia. Anemia has adverse effects on the heart and increases the severity of cardiac conditions, including heart failure and heart attacks.

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.

Pregnancy Complications . Although women of child-bearing age are generally at low risk of heart attack, pregnancy can increase the risk for women with certain health conditions. Pregnant women who have diabetes, high blood pressure, or coronary artery disease are at greater risk of having a heart attack than healthy pregnant women. Smoking can increase the risk of heart attack during pregnancy by eight times. Pregnant women who are over 40 years old are at much greater risk than younger women.

NSAIDs and COX-2 Inhibitors . Nonsteroidal anti-inflammatory drugs (NSAIDs) and COX-2 inhibitors may increase the risk for death in patients who have experienced a heart attack. The risk is greatest at higher dosages. NSAIDs include nonprescription drugs like ibuprofen (Advil, Motrin) and prescription drugs like diclofenac (Cataflam, Voltaren). Celecoxib (Celebrex) is currently the only COX-2 inhibitor that is available in the U.S. It has been linked to cardiovascular risks such as heart attack and stroke. Patients who have had heart attacks should talk to their doctors before taking any of these drugs.

• Review Date: 4/15/2006
• Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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