Angina
Angina, also called angina pectoris, is temporary chest pain or a sensation of pressure that occurs while the heart muscle is not receiving enough oxygen.
In the United States, almost 6.5 million people have angina, and it is newly diagnosed in about 350,000 people each year. Angina tends to develop in women at a later age than in men. On average, angina occurs in about 3.9% of white women, 6.2% of black women, and 5.5% of Hispanic women and in about 2.6% of white men, 3.1% of black men, and 4.1% of Hispanic men.
Narrowing of the arteries due to fatty deposits (atheroma) or occasionally due to another abnormality may interfere with blood flow to the heart muscle and prevent it from receiving enough blood and oxygen. An inadequate blood supply (ischemia) to the heart sometimes causes angina. Angina usually first occurs during physical exertion or emotional distress, which make the heart work harder and increase its need for oxygen. The reduced blood flow through narrowed arteries cannot meet this increased need. If the artery is narrowed enough (usually by more than 70%), angina can occur even at rest, when the demands on the heart are at their minimum.
Not everyone with ischemia experiences angina. Ischemia without angina is called silent ischemia. Doctors do not understand why ischemia is sometimes silent, and some debate its significance. However, most experts consider silent ischemia as serious as ischemia with angina.
Nocturnal angina is angina that occurs at night, during sleep.
Angina decubitus is angina that occurs when a person is lying down (not necessarily only at night) without any apparent cause. Angina decubitus occurs because gravity redistributes fluids in the body. This redistribution makes the heart work harder.
Variant angina results from a spasm of one of the large coronary arteries on the surface of the heart. It is called variant because it is characterized by pain during rest, not during exertion, and by specific changes detected with electrocardiography (ECG) during an episode of angina.
Unstable angina refers to angina in which the pattern of symptoms changes. Because the characteristics of angina in a particular person usually remain constant, any change--such as more severe pain, more frequent attacks, or attacks occurring with less exertion or during rest--is serious. Such change usually reflects a rapid progression of coronary artery disease, with an increasing narrowing of a coronary artery because an atheroma has ruptured or a clot has formed. The risk of a heart attack is high. Unstable angina is a medical emergency.
Causes
Usually, angina results from coronary artery disease.
A sudden temporary constriction of an artery (arterial spasm) may cause angina by abruptly decreasing the supply of blood and thus oxygen. Severe anemia may also cause angina. In anemia, the number of red blood cells (which contain hemoglobin--the molecule that carries oxygen) or the amount of hemoglobin in the cells is below normal. As a result, the oxygen supply to the heart muscle is reduced.
Syndrome X is a form of angina caused neither by spasm nor by any apparent blockage in the large coronary arteries. Temporary narrowing of much smaller coronary arteries may be responsible, at least in some people. The reasons for the temporary narrowing are unknown but may involve a chemical imbalance in the heart or abnormalities in the functioning of small arteries (arterioles). This syndrome is sometimes called cardiac syndrome X to distinguish it from another disorder also called syndrome X (metabolic syndrome X or the syndrome of insulin resistance (see Section 12, Chapter 157)).
Unusual causes of angina include severe high blood pressure; narrowing of the aortic valve (aortic valve stenosis); leakage of the aortic valve (aortic valve regurgitation); and thickening of the walls of the ventricles (hypertrophic cardiomyopathy), especially thickening of the wall separating the ventricles (hypertrophic obstructive cardiomyopathy). These conditions increase the amount of work (workload) for the heart and thus the amount of oxygen needed by the heart muscle. When the need for oxygen exceeds the supply, angina results. Abnormalities of the aortic valve may reduce blood flow through the coronary arteries, because the openings of the coronary arteries are located just beyond this valve.
Symptoms
Most commonly, a person feels angina as pressure or an ache beneath the breastbone (sternum). Pain also may occur in either shoulder or down the inside of either arm; through the back; and in the throat, jaw, or teeth. Many people describe the feeling as discomfort or heaviness rather than pain.
In older people, symptoms may be different and therefore easily misdiagnosed. For instance, the pain is less likely to occur beneath the breastbone. Pain may occur in the back and shoulders and may be incorrectly blamed on arthritis. Pain may occur in the stomach area, particularly after meals (because extra blood is needed to help in digestion). Such pain may be called indigestion and blamed on a stomach ulcer. Also, older people who have confusion or dementia may have difficulty in communicating that they have pain.
Symptoms may also be different in women. Women are more likely to have unusual types of chest discomfort.
Typically, angina is triggered by exertion, lasts no more than a few minutes, and subsides with rest. Some people experience angina predictably with a specific degree of exertion. In other people, episodes occur unpredictably. Often, angina is worse when exertion follows a meal. It is usually worse in cold weather. Walking into the wind or moving from a warm room into the cold air may trigger angina. Emotional stress may also cause or worsen angina. Sometimes, experiencing a strong emotion while resting or having a bad dream during sleep can cause angina.
Diagnosis
Doctors diagnose angina largely based on a person's description of the symptoms. A physical examination and electrocardiography (ECG) (see Section 3, Chapter 21) may detect little, if anything, abnormal between and sometimes even during attacks of angina, even in people with extensive coronary artery disease. During an attack, the heart rate may increase slightly, blood pressure may go up, and with a stethoscope, doctors may hear a change in the heartbeat. ECG may detect changes in the heart's electrical activity.
When symptoms are typical, the diagnosis is usually easy for doctors. The kind of pain, its location, and its association with exertion, meals, weather, and other factors help doctors make the diagnosis. The presence of risk factors for coronary artery disease also helps establish the diagnosis. If a person experiences chest pain during the examination, a doctor may place a dose of nitroglycerin (a drug that dilates blood vessels) under the person's tongue as a test; if the pain is due to angina, relief should occur in less than 3 minutes.
The following procedures may help evaluate the inadequate blood supply (ischemia) to the heart muscle and determine whether coronary artery disease is present and how extensive it is.
For exercise stress testing (see Section 3, Chapter 21), the person walks on a treadmill or rides a stationary bicycle while being monitored by ECG. This procedure can help doctors determine whether coronary angiography or coronary artery bypass surgery is needed. If people cannot exercise, testing is performed after a drug that makes the heart work harder is injected.
For radionuclide imaging (see Section 3, Chapter 21), a tiny amount of a radioactive substance is injected into a vein. Radionuclide imaging can identify the location and extent of ischemia and show the amount of blood reaching the heart muscle. This procedure may be combined with stress testing.
Echocardiography (see Section 3, Chapter 21) uses ultrasound waves to produce images of the heart (echocardiograms). This procedure shows heart size, movement of the heart muscle, blood flow through the heart valves, and valve function. Echocardiography is performed during rest and exercise. When ischemia is present, the pumping motion of the left ventricle is abnormal.
For coronary angiography (see Section 3, Chapter 21), x-rays of arteries are taken after a radiopaque dye is injected. Coronary angiography, the most accurate procedure for diagnosing coronary artery disease, may be performed when a diagnosis is uncertain. Coronary angiography is commonly used to help evaluate whether coronary artery bypass surgery or angioplasty is appropriate. Angiography can also detect spasm of an artery. A drug that can produce a spasm may be used during angiography if a spasm does not occur.
In a few people who have typical symptoms of angina and abnormal results on an exercise stress test, coronary angiography does not confirm the presence of coronary artery disease. Some of these people have syndrome X, but for most, the source of the symptoms does not involve the heart.
Continuous ECG monitoring with a Holter monitor (see Section 3, Chapter 21) may detect abnormalities indicating symptomatic or silent ischemia or variant angina (which typically occurs during rest).
Prognosis
Key factors that can worsen the outcome (prognosis) for people who have angina include advancing age, extensive coronary artery disease, diabetes, the presence of other risk factors (particularly smoking), severe pain, and, most important, reduced pumping ability of the heart (ventricular function). For example, the more coronary arteries affected or the larger the blockage of the arteries, the worse the prognosis. The prognosis is surprisingly good for people with stable angina and normal pumping ability. Reduced pumping ability dramatically worsens the prognosis. The prognosis for people with syndrome X does not differ from that for people without coronary artery disease.
The death rate each year for people with angina and no other risk factors is about 1.4%. The rate is higher for people with risk factors such as high blood pressure, abnormal ECG results, or a previous heart attack.
Treatment
Treatment begins with attempts to slow the progression of coronary artery disease or to reverse it by dealing with risk factors. Risk factors, such as high blood pressure and high cholesterol levels, are treated promptly. Quitting smoking is crucial. A low-fat, varied diet and exercise (for most people) are recommended. Weight loss, if needed, is also recommended.
Treatment of angina depends partly on the stability and severity of the symptoms. When symptoms are stable and mild to moderate, the most effective treatment may be modification of risk factors and the use of certain drugs. When symptoms worsen rapidly, immediate hospitalization is usually also required. If lifestyle changes (including a change in diet) to modify risk factors and drug therapy do not cause symptoms to subside markedly, angiography may be used to determine if coronary artery bypass surgery or angioplasty is needed and feasible. However, surgical techniques are only mechanical measures for correcting the immediate problem. They do not cure the underlying disease. To improve their overall prognosis, people still need to modify risk factors. For example, lowering LDL cholesterol levels as much as possible using drugs may reduce angina as effectively as angioplasty over a period of 6 months or more.
Treatment of stable angina is designed to prevent or reduce ischemia and to minimize symptoms. Five types of drugs are available: beta-blockers, nitrates, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, and antiplatelet drugs.
People with syndrome X are usually given nitrates or beta-blockers to relieve symptoms.
People with unstable angina should usually be hospitalized, so that doctors can closely monitor drug therapy and use other therapies if necessary. These people are given drugs that reduce the clotting tendency of blood. These drugs include heparin (an anticoagulant given intravenously) and aspirin (an antiplatelet drug). People with an allergy to aspirin may be given ticlopidine or clopidogrel instead. A glycoprotein IIb/IIIa inhibitor (another type of antiplatelet drug), such as abciximab and tirofiban, may also be given. Beta-blockers and intravenous nitroglycerin are given to reduce the workload of the heart. If drug therapy is not effective, coronary angiography followed, if possible, by angioplasty or coronary artery bypass surgery may be necessary. Doctors may decide to perform angioplasty or coronary artery bypass surgery after they consider many factors, including the severity of disease and the characteristics of the person (including age).
Drug Therapy
Beta-blockers interfere with the effects of the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) on the heart and other organs. These hormones stimulate the heart to beat faster and more forcefully and most arterioles to constrict (causing blood pressure to increase (see Section 3, Chapter 22)). Thus, beta-blockers reduce the resting heart rate and blood pressure. During exercise, they limit the increase in heart rate and in blood pressure and so reduce the demand for oxygen. Beta-blockers reduce the risk of heart attacks and sudden death, improving the long-term outcome for people with coronary artery disease.
Nitrates, such as nitroglycerin, dilate blood vessels. Either short-acting or long-acting nitrates can be taken. Taking nitroglycerin, a short-acting nitrate, usually relieves an episode of angina in 1 to 3 minutes; the effects last 30 minutes. Nitroglycerin is usually taken as a tablet placed under the tongue (sublingual administration) or as a spray inhaled through the mouth. Alternatively, the tablet may be placed next to the gum. People with chronic stable angina should keep nitroglycerin tablets or spray with them at all times. Taking nitroglycerin just before reaching a level of exertion known to induce angina may be useful.
Long-acting nitrates (such as isosorbide) are taken by mouth 1 to 4 times a day. Nitrate skin patches and paste, in which the drug is absorbed through the skin over many hours, are also effective. Long-acting nitrates taken regularly can soon lose their ability to provide relief. Most experts recommend that people not take the drug for an 8- to 12-hour period each day, usually at night unless that is when angina occurs. This approach helps maintain the long-term effectiveness of the drug. Unlike beta-blockers, nitrates do not reduce the risk of heart attacks and sudden death, but they greatly reduce symptoms in people with coronary artery disease.
Calcium channel blockers prevent blood vessels from narrowing (constricting) and can counter coronary artery spasm. These drugs are also effective in treating variant angina. All calcium channel blockers reduce blood pressure. Some of these drugs, such as verapamil and diltiazem, may also reduce the heart rate. This effect can be useful to many people, especially those who cannot take beta-blockers.
ACE inhibitors, such as ramipril, are often given to people who have evidence of coronary artery disease, including angina. These drugs can reduce the risk of heart attack and of death due to coronary artery disease.
Antiplatelet drugs, such as aspirin, ticlopidine, and clopidogrel, modify platelets so that they do not clump on blood vessel walls. Platelets, which circulate in the blood, promote clot formation (thrombosis) when a blood vessel is injured. However, when platelets collect on atheromas in an artery's walls, the resulting clot can narrow or block the artery and result in a heart attack. Aspirin modifies platelets irreversibly and thus reduces the risk of death from coronary artery disease. Doctors recommend that most people who have coronary artery disease take one baby aspirin, one half of an adult aspirin, or one full adult aspirin daily to reduce the risk of a heart attack. People with an allergy to aspirin may take ticlopidine or clopidogrel as an alternative. Antiplatelet drugs are given to people with angina unless there is a reason not to; for example, they are not given to people who have a bleeding disorder.
 See the drug table Drugs Used to Treat Coronary Artery Disease.
Coronary Angioplasty
Generally, angioplasty (also called percutaneous transluminal coronary angioplasty--PTCA) is preferred to bypass surgery because it is a less invasive procedure. However, the affected area of the coronary artery may not be suited to angioplasty because of its location, its length, the amount of calcium that accumulates, or other conditions. Thus, doctors carefully determine whether a person is a good candidate for the procedure. When the affected area is clearly defined or the person is critically ill, angioplasty may be performed during angiography. The person is usually awake during the procedure.
 See the figure Understanding Angioplasty.
Less than 1 to 2% of people die during angioplasty, and 3 to 5% have nonfatal heart attacks. Coronary artery bypass surgery becomes necessary immediately after angioplasty for 2 to 4% of people.
For the procedure, a large needle is inserted into a large peripheral artery, usually the main artery of the thigh (femoral artery). Then a long guide wire is threaded through the needle, into the artery, and eventually through the aorta into the narrowed coronary artery. A catheter with a balloon attached to the tip is threaded over the guide wire and into the narrowed coronary artery. The catheter is positioned so that the balloon is at the level of the narrowing. The balloon is then inflated for several seconds. Inflation and deflation may be repeated several times.
The person is closely monitored during the procedure because balloon inflation momentarily blocks blood flow in the affected coronary artery. This blockage can produce chest pain and changes in the heart's electrical activity (detected by ECG) in some people. The inflated balloon compresses the atheroma that is narrowing the artery and widens the artery. When angioplasty is successful, the narrowing is greatly reduced. In 80 to 90% of people, the narrowed arteries that are reached are opened.
In about 20 to 30% of people, the coronary artery becomes blocked again within 6 months--often within the first few weeks after the procedure. A second angioplasty is often performed and may successfully control coronary artery disease over the long term. To keep the artery open, doctors may insert a tube made of wire mesh (a stent) into the artery. This procedure appears to reduce the risk of a subsequent narrowing in the same place by half. Stents are used in 60 to 85% of people who undergo angioplasty.
Few studies have compared the results of angioplasty with drug therapy. Success rates of angioplasty are thought to be similar to those of bypass surgery. In a study comparing bypass surgery with angioplasty, recovery time was shorter after angioplasty, and the risk of death and heart attack remained about the same over the 21/2 years of the study. People who have diabetes appear to have a better outcome with bypass surgery than with angioplasty.
 See the animation Understanding Angioplasty.
Coronary Artery Bypass Surgery
This surgery, commonly called bypass surgery, is highly effective for people who have angina and coronary artery disease. It can improve exercise tolerance, relieve symptoms, and decrease the number or dose of drugs needed. Bypass surgery is most likely to benefit people who have severe angina that is not relieved by drug therapy, a normally functioning heart, no previous heart attacks, and no other conditions that would make surgery hazardous (such as chronic obstructive pulmonary disease). For such people, bypass surgery that is not performed on an emergency basis carries a risk of death of 1% or less and a risk of heart damage (such as a heart attack) during surgery of less than 5%. About 85% of people have complete or dramatic relief of symptoms after surgery.
 See the figure Coronary Artery Bypass Surgery.
The risks from surgery are somewhat higher for people with reduced pumping ability of the heart (poor left ventricular function), damaged heart muscle from a previous heart attack, or other cardiovascular problems. However, if these people survive the surgery, their prospects for long-term survival are improved.
Bypass surgery consists of grafting veins or arteries from another part of the body to a coronary artery and to the aorta (the major artery that takes blood from the heart to the rest of the body). Blood flow is thus rerouted, skipping over (bypassing) the narrowed or blocked area. Veins are usually taken from the leg. Arteries are usually taken from beneath the breastbone (sternum) or from the forearm. Artery grafts rarely develop coronary artery disease, and more than 90% of them still work properly 10 years after the bypass surgery. However, vein grafts may gradually become narrowed by atheromas, and after 5 years, one third or more may be completely blocked.
The operation takes 2 to 4 hours, depending on the number of blood vessels to be grafted. A numeric modifier (for example, triple or quadruple) before bypass refers to the number (3 or 4) of arteries that are bypassed. The person is given a general anesthetic. Then, an incision is made down the center of the chest from the neck to the top of the stomach, and the breastbone is parted. This type of surgery is called open-heart surgery. Usually, the heart is stopped so that it is not moving and thus easier to operate on. A heart-lung machine is then used to pump blood through the bloodstream. When only one or two blood vessels require grafting, the heart may be left pumping. The hospital stay is typically 5 to 7 days, usually less if a heart-lung machine was not used during surgery.
With new techniques, chest incisions can be much smaller, resulting in minimally invasive coronary artery bypass surgery. One technique involves robotics. While sitting at a computer console, a surgeon uses pencil-sized robotic arms to perform the operation. The arms hold specially designed surgical instruments that can perform intricate movements, mimicking those of the surgeon's hands. Through a viewing scope, the surgeon watches a magnified three-dimensional image of the operation. Thus, the surgeon does not need to be in the same room as the patient. The operation requires three 1-inch incisions--one for each of the two robotic arms and one for a camera, which is connected to the scope. The operating time and hospital stay are usually shorter with the new procedures than with open-heart surgery.
In an experimental technique (called percutaneous in situ coronary venous arterialization), bypass is performed without surgery. A catheter is threaded to the blocked or narrowed coronary artery and used to make a connection between the artery and a nearby coronary vein. The vein then functions as an artery, supplying blood to the heart.
Other Techniques
New techniques to remove atheromas include the use of tiny blades, burrs, or lasers to remove thick, fibrous, and calcified atheromas by cutting, shaving, crushing, or dissolving them. Some of these techniques are still being evaluated, but so far, the results, especially over the long term, have been disappointing.
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