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Updated 17 December 2010

Angina

Angina is the chest discomfort or pain that occurs when the oxygen supply to an area of the heart muscle does not meet the demand.

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Summary

  • Angina and heart attack are two of the most serious causes of chest pain.
  • Angina is a result of inadequate oxygen supply to the heart muscle.
  • Treatment of angina includes rest, medications, angioplasty, and/or coronary artery bypass surgery.
  • Life-style modification is important in both primary and secondary prevention and includes smoking cessation and control of hypercholesterolaemia (high cholesterol).

Description

Angina is the chest discomfort or pain that occurs when the oxygen supply to an area of the heart muscle does not meet the demand. Oxygen is carried to the heart muscle by the coronary arteries running around the heart.

Cause

The most common cause of angina is coronary artery disease. A less common cause is spasm of the coronary arteries. Coronary arteries supply oxygenated blood to the heart muscle.

Coronary artery disease

Coronary artery disease is the result of cholesterol deposits on the artery wall, causing the formation of hard, thick plaques. The accumulation of cholesterol plaques over time causes narrowing of the coronary arteries, a process called atherosclerosis.

Smoking, high blood pressure, elevated cholesterol and diabetes can accelerate atherosclerosis. A genetic predisposition to the development of atherosclerosis is also found in some families.

When coronary arteries become narrowed by more than 50 to 70 percent, they can no longer meet the increased blood oxygen demand by the heart muscle during exercise or stress. Lack of oxygen to the heart muscle causes chest pain (angina).

The plaques can also rupture, exposing elements that initiate blood clotting inside the artery. These blood clots can completely block the artery, cutting off the blood supply to an area of heart muscle completely. This causes death of a part of the heart muscle, called heart attack.

Spasm of the coronary arteries

Muscle fibres surround artery walls. Contraction of these fibres causes a sudden narrowing (spasm) of the artery. A spasm of the coronary arteries reduces blood to the heart muscle and also causes angina.

This type of angina is relatively uncommon, typically occurring at rest. It can awaken you from sleep. People with this type of angina are often slightly younger – in their thirties and forties.

Symptoms

  • Angina is usually felt as squeezing, pressure, heaviness, tightening, or aching across the chest, usually in the middle of the chest. The pain often radiates to the neck, jaw, arms, back, or even the teeth. It may feel like indigestion or heartburn.
  • Associated symptoms include weakness, sweating, nausea and shortness of breath.
  • Angina usually occurs during exertion, severe emotional stress, or after a heavy meal. During these periods, the heart muscle demands more blood oxygen than the narrowed coronary arteries can deliver.
  • Angina typically lasts one to 15 minutes and is relieved by rest or by placing a nitro-glycerine tablet under the tongue. If the pain lasts longer than 15 minutes, it may signify a heart attack.

When to see a doctor

Angina is usually a warning sign of the presence of significant underlying coronary artery disease limiting oxygen supply to the heart muscle. Those with angina are at risk of developing a heart attack (myocardial infarction). A heart attack is the death of heart muscle precipitated by the complete blockage of a diseased coronary artery by a blood clot.

During angina, the lack of oxygen (ischaemia) to the heart muscle is temporary and reversible. On the other hand, the muscle damage accompanying heart attack is permanent. The dead muscle turns into scar tissue when it heals. A scarred heart cannot pump blood as efficiently as a normal heart, and can lead to heart failure.

Most people who have been diagnosed with angina have a pattern to their angina attacks that they can recognise. Call your nearest emergency services immediately if:

  • The pain gets worse
  • The pain does not go away
  • The pain occurs with less exertion
  • You are unsure of how to use your medication
  • You are having angina symptoms now, but are not under treatment

Diagnosis

Angina is diagnosed with the aid of a number of investigations

  • Electrocardiology (ECG)
  • Stress ECG
  • Stress echocardiology
  • Thallium scan
  • Cardiac angiography
  • Ultrafast CAT scan
  • MRI imaging

Electrocardiography (ECG)

The resting electrocardiogram is a recording of the electrical activity of the heart muscle, detected by electrodes attached to the extremities and the chest wall. This non-invasive, inexpensive test can detect heart muscle that is in need of oxygen.

The resting ECG is useful in showing the changes that are caused by a heart attack. It is less useful in patients with angina, since the chest pain and lack of oxygen supply to the heart only become evident during times of increased oxygen demand such as when exercising.

Stress electrocardiography

An exercise or stress electrocardiogram (ECG) evaluates the heart’s response to the stress of physical exercise. This test, also called the treadmill test, is performed to determine the cause of chest pain in a patient with a normal resting ECG.

The electrical activity of the heart, blood pressure and heart rate are monitored while you walk on a motor-driven treadmill or pedal a stationary bicycle. The occurrence of chest pain during exercise can be correlated with changes on the ECG that demonstrate the lack of oxygen to the heart muscle. The accuracy of exercise treadmill tests in the diagnosis of significant coronary artery disease is 60 to 70%.

If you cannot undergo an exercise stress test because of neurologic or arthritic difficulties, medications can be injected intravenously to simulate the stress on the heart normally brought on by exercise.

Stress echocardiography combines ultrasound imaging of the heart muscle with exercise treadmill testing.

When a coronary artery is significantly narrowed, the heart muscle supplied by this artery does not contract as well as the rest of the heart muscle during exercise. Abnormalities in muscle contraction can be detected by echocardiography.

Stress echocardiography is about 80 to 85% accurate – more accurate than an exercise treadmill test – in detecting coronary artery disease.

Thallium scan

If the exercise treadmill test does not show signs of coronary artery disease, a nuclear agent (thallium) can be given intravenously during exercise treadmill tests. A special camera then measures the amount of radioactivity that reaches the heart muscle.

A decreased blood flow in an area of the heart muscle during exercise, with normal blood flow to the area at rest, signifies significant artery narrowing in that region of the heart.

Thallium stress tests are about 80 to 85% accurate in detecting significant coronary artery disease.

Cardiac angiography

Cardiac catheterisation with angiography (coronary arteriography) is used to determine the severity and location of blocked arteries supplying the heart with blood and oxygen.

The test is accomplished by inserting a thin, hollow, flexible tube into an artery in the groin or arm. The catheter is then gently threaded along this artery until it reaches the heart. Iodine contrast "dye" is injected into the coronary arteries while an X-ray video is recorded. A number of tests and measurements can be performed.

Coronary arteriography is the most accurate test to detect coronary artery narrowing. It gives the doctor a picture of the location and severity of coronary artery disease. This information can be important in helping doctors select treatment options.

Ultrafast CAT scan

A newly developed, non-invasive computerised axial tomography scan (ultrafast CAT scan) uses computer-analysed X-rays to detect small amounts of calcium in the plaque of coronary arteries. If an ultrafast CAT scan shows no calcium in the arteries, atherosclerotic coronary artery disease is unlikely.

Ultrafast CAT scanning is useful in evaluating chest pain in younger people (men under 40 and women under 50 years old). Since young people do not normally have significant coronary artery plaque, a negative ultrafast CAT scan makes the diagnosis of coronary artery disease unlikely. However, it is less meaningful in older people, who are likely to have mild plaques simply from the ageing process.

MRI imaging

Magnetic resonance imaging (MRI) uses magnetic fields to produce an image of the blood vessels. Currently, the larger vessels, such as the carotid arteries in the neck, can be imaged using this technique. Over the next five to 10 years, software and hardware improvements may allow screening of the heart's arteries with this method.

Treatment

Medication

The following medications are commonly used to treat angina

  • Nitro-glycerine
  • Beta-blockers
  • Calcium channel blockers

Nitro-glycerine
Sublingual (placed under the tongue) nitro-glycerine tablets, commonly known as TNT tablets, relieve angina by reducing the heart muscle's demand for oxygen. Nitro-glycerine also relieves spasm of the coronary arteries and can redistribute coronary artery blood flow to areas that need it most.

Short-acting nitro-glycerine can be repeated at five-minute intervals. When three doses of nitro-glycerine fail to relieve the angina, immediate medical attention is recommended. Short-acting nitro-glycerine can also be used prior to exertion to prevent angina. Due to their volatility, these tablets may easily lose their potency if stored incorrectly. It is therefore important to follow the storage instructions carefully.

Longer-acting nitro-glycerine preparations are useful in preventing and reducing the frequency and intensity of episodes in people with chronic angina. Headaches, light-headedness and even fainting due to excess lowering of blood pressure may limit the use of nitro-glycerine preparations.

Beta-blockers
Beta-blockers have an inhibiting effect on adrenaline, which makes them useful in the treatment of angina. Inhibition of adrenaline reduces the heart muscle's demand for oxygen by decreasing the heart rate, lowering the blood pressure, and reducing the pumping force of the heart muscle.

Beta-blockers include propranolol and atenolol.

Possible side effects include:

  • Worsening of asthma
  • Excess lowering of the heart rate and blood pressure with associated dizziness
  • Depression
  • Impotence
  • Increased cholesterol levels
  • Diminished heart muscle function, resulting in the accumulation of fluid in the lungs and consequently shortness of breath

Calcium channel blockers
Calcium channel blockers relieve angina by lowering blood pressure and reducing the pumping force of the heart muscle, thereby reducing muscle oxygen demand. Calcium channel blockers also relieve coronary artery spasm.

Calcium channel blockers include nifedipine, verapamil, and diltiazem.

Side effects include

  • Swelling of the legs
  • Excess lowering of the heart rate and blood pressure
  • Diminished heart muscle function, resulting in the accumulation of fluid in the lungs and consequently shortness of breath

It is important to consult with your doctor before changing angina medication.

Surgery

Although most coronary artery disease is treated with medication, surgical treatment to open up or replace narrowed arteries may be needed if symptoms are severe or not controlled by medication. It may also be used if tests show there are blocked arteries in the heart that may soon close off and lead to a heart attack.

The goals of surgical treatment are to restore blood flow to the heart muscle, relieve chest pain (angina), prevent heart attack, and allow the person to maintain or resume an active lifestyle.

Balloon angioplasty
Depending on the location and severity of the disease in the coronary arteries, some people are referred for balloon angioplasty (percutaneous transluminal coronary angioplasty).

During the angioplasty procedure a flexible, thin tube (catheter) is inserted through an artery in the groin or arm and threaded into the heart artery that is narrowed. Once the tube reaches the narrowed artery, a small balloon at the end of the tube is inflated for 20 seconds to three minutes. The pressure from the inflated balloon presses the fat and calcium (plaque) against the wall of the artery to improve blood flow.

Once the fat and calcium build-up is compressed, a small, expandable wire tube called a stent is sometimes inserted into the artery to hold it open. Re-closure (restenosis) of the artery is less likely with stenting than with angioplasty alone.

Coronary artery bypass graft surgery
Other patients are referred for coronary artery bypass graft surgery to increase coronary artery blood flow.

Under general anaesthesia, a lengthways cut is made in the chest over the breastbone. The breastbone is divided, and the ribs are spread open so the surgeon can reach the heart. If a vein is needed to serve as a bypass blood vessel, additional surgery on the leg is required to remove a vein.

During surgery the heart is stopped with a chemical solution and cooled. Blood is pumped through a heart-lung machine that circulates and oxygenates the blood in the body while your heart is being repaired. The vein taken from elsewhere in the body is sewn to the heart to bypass the narrowed or blocked section of coronary artery. The heart is warmed and given a mild electric shock to reactivate the heartbeat. Surgical wires are used to rejoin the breastbone edges. The chest muscles and skin are closed with surgical thread.

From opening to closing the chest, the operation takes 30 to 45 minutes. It also requires one to two hours of preparation and one to two hours of observation after the procedure.

Prevention

Rather than waiting for warning signs of cardiovascular disease, think about what you can do now to prevent it. Even if you have been diagnosed with angina or have had a heart attack, you can still play an active role in preventing disease progression.

The following life-style modifications are of proven benefit:

  • Don't smoke. The more cigarettes you smoke, the higher your heart disease risk.
  • Avoid foods that contain saturated fat and cholesterol. Limit fat to 30% of your daily calories by balancing occasional high-fat foods with low-fat choices, such as fruits, vegetables and grains.
  • Control your blood pressure and blood cholesterol levels. Small elevations in blood pressure above 140/90 mm Hg can double your cardiovascular disease risk.
  • Exercise. Choose aerobic activity such as brisk walking, swimming, jogging or cycling. Gradually work up to exercising 30 to 45 minutes at least three times a week.
  • Control your sugar. If you are diabetic, make sure your sugar control is as strict as possible since this will also delay the process of atherosclerosis.

Reviewed by Dr Mark Abelson MBBCH, MRCP(UK), FCP(SA)

 
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