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Angina

(Angina Pectoris)

By Jonathan G. Howlett, MD, University of Calgary;Canadian Heart Failure Society

Angina is temporary chest pain or a sensation of pressure that occurs while the heart muscle is not receiving enough oxygen.

  • A person with angina has discomfort or pressure beneath the breastbone (sternum).

  • Angina typically occurs in response to exertion and is relieved by rest.

  • Doctors diagnose angina based on symptoms, electrocardiography, and imaging tests.

  • Treatment may include nitrates, beta-blockers, calcium channel blockers, and percutaneous coronary intervention or coronary artery bypass graft surgery.

In the United States, about 10 million people have angina, and it is newly diagnosed in about 500,000 people each year. Angina tends to develop in women at a later age than in men.

Causes of Angina

The heart muscle needs a constant supply of oxygen-rich blood. The coronary arteries, which branch off the aorta just after it leaves the heart, deliver this blood. Usually, angina occurs when the heart’s workload (and need for oxygen) exceeds the ability of the coronary arteries to supply an adequate amount of blood to the heart. Coronary blood flow can be limited when the arteries are narrowed (see Overview of Coronary Artery Disease). Narrowing usually results from fatty deposits in the arteries (atherosclerosis) but may result from coronary artery spasm. Inadequate blood flow to any tissue is termed ischemia.

When angina is due to atherosclerosis, it usually first occurs during physical exertion or emotional distress, which make the heart work harder and increase its need for oxygen. 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.

Severe anemia increases the likelihood of 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.

Unusual causes

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 or the syndrome of insulin resistance).

Other unusual causes of angina include the following:

  • Severe high blood pressure

  • Narrowing of the aortic valve (aortic valve stenosis)

  • Leakage of the aortic valve (aortic valve regurgitation)

  • Thickening of the walls of the ventricles (hypertrophic cardiomyopathy), especially thickening of the wall separating the ventricles (hypertrophic obstructive cardiomyopathy)

These conditions increase the heart’s workload 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.

Classification of Angina

Nocturnal angina is angina that occurs at night, during sleep.

Stable angina is chest pain or discomfort that typically occurs with activity or stress. Episodes of pain or discomfort are provoked by similar or consistent amounts of activity or stress.

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 sudden 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 considered an acute coronary syndrome.

Symptoms of Angina

Most commonly, a person feels angina as pressure or an ache beneath the breastbone (sternum). People often interpret the sensation as discomfort or heaviness rather than pain. Discomfort also may occur in either shoulder or down the inside of either arm, through the back, and in the throat, jaw, or teeth.

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. Discomfort, bloating, and gas may occur in the stomach area, particularly after meals (because extra blood is needed to help in digestion). People may mistake such discomfort for indigestion or blame it on a stomach ulcer. Belching may even seem to relieve these symptoms. Also, older people who have confusion or dementia may have difficulty in communicating that they have pain.

Symptoms may be very different in women. Women are more likely to have a burning sensation or tenderness in the back, shoulders, arms, or jaw.

Did You Know...

  • Women experience the discomfort of angina differently than men and are more likely to have a burning sensation or tenderness in the back, shoulders, arms, or jaw.

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.

Silent ischemia

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.

Diagnosis of Angina

  • Electrocardiography

Doctors diagnose angina largely based on a person’s description of the symptoms. A physical examination and electrocardiography (ECG) 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 to make. 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.

Doctors may do other procedures to evaluate the inadequate blood supply (ischemia) to the heart muscle and determine whether coronary artery disease is present and how extensive it is.

Stress testing

Stress testing (also called exercise tolerance testing) is based on the principle that if the coronary arteries are only partly blocked, the heart may have an adequate blood supply when the person is resting but not when the heart is working hard. For stress testing, the person's heart is made to work hard by exercise (for example, walking on a treadmill or riding a stationary bicycle. People who cannot do such exercise are given stimulant drugs that make the heart beat faster. During the stress test, the person is monitored by ECG to look for abnormalities that suggest ischemia.

After the stress, doctors often do more accurate but more expensive tests, such as echocardiography and radionuclide imaging to look for ischemia. These procedures can help doctors determine whether coronary angiography or coronary artery bypass grafting (CABG) is needed.

Echocardiography

Echocardiography 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 done during rest and exercise. When ischemia is present, the pumping motion of the left ventricle is abnormal.

Coronary angiography

For coronary angiography, 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 done when a diagnosis is uncertain. Coronary angiography is commonly used to help evaluate whether CABG or percutaneous coronary intervention (PCI) is appropriate. Angiography can also detect spasm of an artery. A drug that can cause 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 a 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

Continuous ECG monitoring with a Holter monitor may detect abnormalities indicating symptomatic or silent ischemia or variant angina (which typically occurs during rest).

Imaging of the heart

Electron beam computed tomography (CT) can detect the amount of calcium deposits in the coronary arteries. The amount of calcium present (the calcium score) is roughly proportional to the likelihood of the person having angina or a heart attack. However, because calcium deposits may be present even in people whose arteries are not very narrowed, the score does not reliably predict the need for PCI or CABG. Electron beam CT is not recommended for screening all people, in part because it exposes people to a significant amount of radiation. However, the test is often valuable for evaluating people who have a relatively high risk of death or heart attack. People at risk include those who have diabetes, high blood pressure, or both, who have high cholesterol levels, and who have abnormal or unclear stress test results.

Multidetector row CT uses a high-speed CT scanner with many small detectors that can accurately identify coronary artery narrowing. The technique is noninvasive and highly accurate in excluding coronary artery narrowing as a source of a person’s symptoms (particularly in those who were not able to have a stress test or had a stress test that was inconclusive). It can also be used to determine whether a stent or bypass graft is unobstructed, to display cardiac and coronary venous anatomy, and to assess whether atheromas contain calcium. However, the technique cannot be used in women who are pregnant or in people who are unable to hold their breath for 15 to 20 seconds three or four times during the procedure. Also, because the test does not work well if the heart is beating fast, people whose heart rate is above 65 beats per minute are given drugs to slow the heart rate. People who cannot tolerate such drugs or a low heart rate cannot have the test. People are also exposed to significant amounts of radiation.

Cardiac magnetic resonance imaging (MRI) is valuable in evaluating the heart and the large vessels coming from the heart (the aorta and the pulmonary arteries). This technique avoids any radiation exposure. In people with coronary artery disease, MRI may be used to evaluate narrowing of the arteries, measure the blood flow in the coronary arteries, and test how well the heart is being supplied with oxygen. MRI can also be used to assess abnormalities of heart wall motion during stress (which may indicate poor blood supply to that area) and whether areas of heart muscle damaged by a heart attack may recover (testing viability).

Prognosis

Key factors that can worsen the outcome (prognosis) for people who have angina include old age, extensive coronary artery disease, diabetes, other risk factors (particularly smoking), severe pain, and, most importantly, 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 is 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, particularly in those who have diabetes.

Treatment of Angina

  • Lifestyle changes

  • Drug therapy

  • Sometimes treatment to open clogged blood vessels (revascularization therapy)

Treatment begins with attempts to slow or reverse the progression of coronary artery disease 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 that is low in simple sugar carbohydrates 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. If modification of risk factors and drug therapy do not cause symptoms to subside markedly, a procedure to restore blood flow to affected areas of the heart (a revascularization procedure) may be needed. When symptoms worsen rapidly, immediate hospitalization is usually required and the person is evaluated for an acute coronary syndrome.

Drug Therapy

Doctors do several types of treatment for people with angina. Different treatments are used to help

  • Resolve an attack of angina (nitrates)

  • Prevent angina from occurring (beta-blockers, calcium channel blockers, sometimes a newer drug, ranolazine)

  • Prevent and reverse coronary artery blockage (angiotensin-converting enzyme [ACE] inhibitors, angiotensin II receptor blockers, statins, and antiplatelet drugs)

Nitrates

Nitroglycerin is a very short-acting nitrate drug that dilates blood vessels. Taking nitroglycerin usually relieves an episode of angina in 11/2 to 3 minutes, and 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.

Beta-blockers

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 cause most arterioles to constrict (causing blood pressure to increase—see Drug therapy). 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 and decrease the likelihood of angina. Beta-blockers also reduce the risk of heart attacks and sudden death, improving the long-term outcome for people with coronary artery disease.

Calcium channel blockers

Calcium channel blockers prevent blood vessels from narrowing (constricting) and can counter coronary artery spasm. In addition to treatment of stable angina, 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. Reducing blood pressure and heart rate reduces the demand for oxygen and decreases the likelihood of angina. This effect can be useful to many people, especially those who cannot take beta-blockers or who do not get enough relief from nitrates.

Angiotensin converting enzyme inhibitors and angiotensin II receptor blockers

Angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor blockers are often given to people who have evidence of coronary artery disease, including angina. These drugs do not treat angina itself, but they can reduce blood pressure (and so the work the heart has to do to pump blood) and also they reduce the risk of heart attack and of death due to coronary artery disease.

Statins

Statins are drugs that lower blood levels of LDL cholesterol, the type of cholesterol that can cause coronary artery disease. These drugs reduce the chance of heart attack, stroke, and death.

Antiplatelet drugs

Antiplatelet drugs, such as aspirin, ticlopidine, and clopidogrel, modify platelets so that they do not clump and stick 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 reduces the risk of death from coronary artery disease. Doctors recommend that most people who have coronary artery disease take aspirin daily to reduce the risk of a heart attack. Prasugrel, clopidogrel, and ticagrelor also further modify platelets in addition to aspirin. One of these drugs may be used in addition to aspirin for a period of time after a heart attack or PCI to reduce the chances of a future heart attack. An antiplatelet drug is usually 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.

More information on the specific drugs for coronary artery disease can be found elsewhere in The Manual (see Table: Drugs Used to Treat Coronary Artery Disease*).

Revascularization Procedures

People who continue to have angina despite use of preventive drugs sometimes benefit from procedures that open up or replace (bypass) the coronary arteries. These procedures are termed revascularization and include

  • Percutaneous coronary intervention (PCI) procedures (also called angioplasty)

  • Coronary artery bypass grafting (CABG)

These invasive techniques are effective, but they are only mechanical measures for correcting the immediate problem. They do not stop the progression of the underlying disease. People still need to modify risk factors.

Percutaneous coronary intervention

PCI is often preferred to CABG because it is less invasive, although it is not appropriate for every situation. PCI is usually preferred when only one or two arteries are affected and the blocked area is not very long. However, new technology and increasing experience are allowing doctors to use PCI for more and more people.

Coronary artery bypass grafting

CABG 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. CABG 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, CABG that is not done 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.

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