Angina

Angina is chest pain or discomfort that occurs when your heart muscle does not get enough blood. Angina may feel like pressure or a squeezing pain in your chest. The pain may also occur in your shoulders, arms, neck, jaw, or back. It may also feel like indigestion.

Angina is a symptom of coronary artery disease (CAD), the most common type of heart disease. CAD occurs when plaque builds up in the coronary arteries. This buildup of plaque is called atherosclerosis. As plaque builds up, the coronary arteries become narrow and stiff. Blood flow to the heart is reduced. This decreases the oxygen supply to the heart muscle.

Types of Angina

The three types of angina are stable, unstable, and variant (Prinzmetal's). It is very important to know the differences among the types.

• Stable angina. Stable angina is the most common type. It occurs when the heart is working harder than usual.
  • There is a regular pattern to stable angina. After several episodes, you learn to recognize the pattern and can predict when it will occur.
  • The pain usually goes away in a few minutes after you rest or take your angina medicine.
  • Stable angina is not a heart attack but makes it more likely that you will have a heart attack in the future.
• Unstable angina. Unstable angina is a very dangerous condition that requires emergency treatment. It is a sign that a heart attack could occur soon. Unlike stable angina, it does not follow a pattern. It can occur without physical exertion and is not relieved by rest or medicine.
• Variant angina. Variant angina is rare. It usually occurs at rest. The pain can be severe and usually occurs between midnight and early morning. It is relieved by medicine.

Not all chest pain or discomfort is angina. Chest pain or discomfort can be caused by a heart attack, lung problems (such as an infection or a blood clot), heartburn, or a panic attack. However, all chest pain should be checked by a doctor.

Symptoms

Pain and discomfort are the main symptoms of angina. These symptoms

• Are often described as pressure, squeezing, burning, or tightness in the chest
• Usually start in the chest behind the breastbone
• May also occur in the arms, shoulders, neck, jaw, throat, or back
• May feel like indigestion

Some people say that angina discomfort is hard to describe or that they can't tell exactly where the pain is coming from. Symptoms such as nausea, fatigue, shortness of breath, sweating, light-headedness, or weakness may also occur.

Symptoms vary based on the type of angina.

Stable Angina

The pain or discomfort:

• Occurs when the heart must work harder, usually during physical exertion
• Is expected, and episodes of pain tend to be alike
• Usually lasts a short time (5 minutes or less)
• Is relieved by rest or angina medicine
• May feel like gas or indigestion
• May feel like chest pain that spreads to the arms, back, or other areas

Unstable Angina

The pain or discomfort:

• Often occurs at rest, while sleeping at night, or with little physical exertion
• Is unexpected
• Is more severe and lasts longer (as long as 30 minutes) than episodes of stable angina
• Is usually not relieved with rest or angina medicine
• May get continuously worse
• May signal that a heart attack will happen soon

Variant Angina

The pain or discomfort:

• Usually occurs at rest and during the night or early morning hours
• Tends to be severe
• Is relieved by angina medicine

Chest pain that lasts longer than a few minutes and is not relieved by rest or angina medicine may mean you are having—or are about to have—a heart attack. Call 911 right away.

Diagnosis

To find out if you have angina, your doctor will:

• Do a physical exam
• Ask about your symptoms
• Ask about your risk factors and your family history of coronary artery disease (CAD) or other heart disease

Sometimes, your doctor can diagnose angina by noting your symptoms and how they occur. Your doctor may order one or more tests to help make a diagnosis of angina. The tests your doctor may order include:

• EKG (electrocardiogram). This test measures the rate and regularity of your heartbeat. Some people with angina have a normal EKG.
• Stress Test. Some heart problems are easier to diagnose when your heart is working harder and beating faster than when it's at rest. During stress testing, you exercise (or are given medicine if you are unable to exercise) to make your heart work harder and beat faster while heart tests are performed.
• During exercise stress testing, your blood pressure and EKG readings are monitored while you walk or run on a treadmill or pedal a bicycle. Other heart tests, such as nuclear heart scanning or echocardiography, also can be done at the same time. These would be ordered if your doctor needs more information than the exercise stress test can provide about how well your heart is working.
• If you are unable to exercise, a medicine can be injected through an intravenous line (IV) into your bloodstream to make your heart work harder and beat faster, as if you are exercising on a treadmill or bicycle. Nuclear heart scanning or echocardiography is then usually done.
• During nuclear heart scanning, radioactive tracer is injected into your bloodstream, and a special camera shows the flow of blood through your heart and arteries. Echocardiography uses sound waves to show blood flow through the chambers and valves of your heart and to show the strength of your heart muscle.
• Your doctor also may order two newer tests along with stress testing if more information is needed about how well your heart works. These new tests are magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning of the heart. MRI shows detailed images of the structures and beating of your heart, which may help your doctor better assess if parts of your heart are weak or damaged. PET scanning shows the level of chemical activity in different areas of your heart. This can help your doctor determine if enough blood is flowing to the areas of your heart. A PET scan can show decreased blood flow caused by disease or damaged muscles that may not be detected by other scanning methods.
• Chest x ray. A chest x ray takes a picture of the organs and structures inside your chest. These include your heart, lungs, and blood vessels.
• Nuclear heart scan. This test provides your doctor with moving pictures of the blood passing through your heart's chambers and arteries and shows the level of blood flood to the heart muscle. A small amount of a radioactive tracer is injected into your bloodstream through a vein, usually in your arm. A special camera is placed in front of your chest to show where the tracer lights up in healthy heart muscle and where it doesn't light up (in heart muscle that has been damaged or has a blocked artery).
• There are different types of nuclear heart scans. Most scans have two phases—taking pictures of the heart at rest and while it is beating faster (called a stress test), although sometimes only a rest scan is done. Many heart problems show up more clearly when your heart is stressed than when it is at rest. By comparing the nuclear heart scan of your heart at rest to your heart at "stress," your doctor can determine if your heart is functioning normally or not.
• Echocardiogram. This test uses sound waves to create a moving picture of your heart. Echocardiogram provides information about the size and shape of your heart and how well your heart chambers and valves are functioning. The test also can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow.
• There are several different types of echocardiograms, including a stress echocardiogram. During this test, an echocardiogram is done both before and after your heart is stressed either by having you exercise or by injecting a medicine into your bloodstream that makes your heart beat faster and work harder. A stress echocardiogram is usually done to find out if you have decreased blood flow to your heart (coronary artery disease).
• Cardiac catheterization. A thin flexible tube (catheter) is passed through an artery in the groin (upper leg) or arm to reach the coronary arteries. Your doctor can determine pressure and blood flow in the heart's chambers, collect blood samples from the heart, and examine the arteries of the heart by x ray.
• Coronary angiography. This test is done during cardiac catheterization. A dye that can be seen by x ray is injected through the catheter into the coronary arteries. Your doctor can see the flow of blood through your heart and the location of blockages.

Your doctor may also order blood tests, such as:

• A fasting lipoprotein profile to check your cholesterol levels.
• Fasting glucose test to check your blood sugar level.
• C-reactive protein (CRP) test. This blood test measures CRP, a protein in the blood that shows the presence of inflammation. Inflammation is the body's response to injury. High levels of CRP may be a risk factor for CAD.
• A test to check for low hemoglobin in your blood. Hemoglobin is the part of red blood cells that carries oxygen to all parts of your body.

Causes

Angina is caused by reduced blood flow to an area of the heart. This is most often due to coronary artery disease (CAD). Sometimes, other types of heart disease or uncontrolled high blood pressure can cause angina.

In CAD, the coronary arteries that carry oxygen-rich blood to the heart muscle are narrowed due to the buildup of fatty deposits called plaque. This is called atherosclerosis. Some plaque is hard and stable and leads to narrowed and hardened arteries. Other plaque is soft and is more likely to break open and cause blood clots. The buildup of plaque on the inner walls of the arteries can cause angina in two ways:

• By narrowing the artery to the point where the flow of blood is greatly reduced
• By forming blood clots that partially or totally block the artery

The illustration shows a normal artery with normal blood flow (Figure A) and an artery containing plaque buildup (Figure B).

Stable Angina

Physical exertion is the most common cause of pain and discomfort from stable angina. Severely narrowed arteries may allow enough blood to reach the heart when the demand for oxygen is low (such as when you are sitting). But with exertion, like walking up a hill or climbing stairs, the heart works harder and needs more oxygen. Other causes include:

• Emotional stress
• Exposure to very hot or cold temperature
• Heavy meals
• Smoking

Unstable Angina

Unstable angina is caused by blood clots that partially or totally block an artery. If plaque in an artery ruptures or breaks open, blood clots may form. This creates a larger blockage. The clot may grow large enough to completely block the artery and cause a heart attack. Blood clots may form, partly dissolve, and later form again. Chest pain can occur each time a clot blocks an artery.

Variant Angina

Variant angina is caused by a spasm in a coronary artery. The spasm causes the walls of the artery to tighten. This narrows the artery, causing the blood flow to the heart to slow or stop. Variant angina may occur in people with and without CAD. Other causes of spasms in the arteries that supply the heart with blood are:

• Exposure to cold
• Emotional stress
• Medications (vasoconstricting) that constrict or narrow blood vessels
• Cigarette smoking
• Cocaine use

Reference:

National Heart, Lung, and Blood Institute, USA.