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Angina

How Is Angina Diagnosed?

Last updated on:
16/03/2012

Contributing Author: Guy Slowik FRCS

A diagnosis of angina pectoris is based upon a number of factors, including the person's symptoms, his or her medical history, and a physical examination. The physician will want to make sure that the individual's chest pain is caused by angina and not some other condition, such as indigestion. In addition, the physician will want to determine how far coronary artery disease (CAD) has progressed.

Tests used to diagnose angina include:

Electrocardiography (EKG, ECG)

Electrocardiography (EKG, ECG) measures the electrical activity of the heart. To do this, a number of electrodes (small metal plates) are placed on the skin of the arms, legs, and chest. The electrodes detect the electrical signals that are produced by the heart muscle. The signals then are sent by wires to the EKG machine, which records them as "waves" that are printed out on paper.

The EKG provides information on new acute changes or damage to the heart muscle as well as clues to previous changes or damage to the heart muscle. It can reveal previous damage of the heart muscle, such as a mild heart attack that a person may have had without even knowing it. Unfortunately, the EKG does not reliably detect narrowing of the coronary arteries. For this information, the physician must perform additional tests, such as coronary angiography.

The EKG often is normal in people with angina when they are at rest, although it usually changes during an anginal attack. For this reason, EKG testing also may be conducted while the individual is exercising on a stationary bicycle or treadmill or while he or she performs daily activities over a 24-hour period (24-hour EKG).

Chest x-ray

A chest x-ray may be performed to rule out lung disease or other chest abnormalities that may be causing pain. In addition, a chest x-ray will reveal enlargement of the heart, which may be associated with heart muscle damage due to heart attack.

Chest x-ray, like an EKG, cannot identify narrowing within the coronary arteries.

Exercise (stress) test

The exercise tolerance test, also known as a "stress" test, is a method used to measure the heart's response to exercise. During this procedure, the individual is asked to ride a stationary bicycle or walk on a treadmill while a physician takes an electrocardiogram.

  • If a treadmill is used, the pace and steepness of the track will increase every few minutes so that the EKG can detect any changes in heart function during physical stress.
  • If a fixed bicycle is used, the principle is exactly the same.

The physician or trained personnel will ask about angina symptoms during the test to ensure that the person does not overwork his or her heart.

In addition, the person may receive an injection of a radioisotope (a radioactive material) such as thallium, which makes the heart and its vessels visible to a special, computer-linked camera. The camera records how the heart moves and which parts of the heart muscle are short of blood during exercise.

The stress test is the only investigation needed for many people, since it is accurate nearly 90% of the time. But, although this method is useful, it cannot identify exactly where or how severely the coronary arteries are blocked. Therefore, in some cases, the physician may request additional tests such as coronary angiography.

Coronary angiography/cardiac catheterization

Coronary angiography - an outpatient procedure that is performed under local anesthesia by a cardiologist (heart specialist) - shows the precise size and location of blockages within the coronary arteries. The blood pressure within the heart can be measured at the same time.

  • A catheter (fine tube) is inserted into an artery in the forearm or groin, and it is snaked through the blood vessels until it reaches the coronary arteries.
  • Then, dye is pumped through the catheter, so that the heart itself and the coronary arteries are visible on a special video screen.

Coronary angiography can pinpoint narrowing, obstruction, and other abnormalities of the coronary arteries. It is an essential test if the cardiologist is considering angioplasty (blood vessel repair) or coronary artery surgery.

Coronary angiography takes about 30 minutes to perform, and it is quite safe. Most individuals are given antianxiety medication before the procedure, so that they feel calm throughout. Because of the anesthetic (painkiller) used during angiography, there is generally no discomfort.

Ergonovine test

The ergonovine test - otherwise known as a "provocation test" - is not done often, but can be performed if angina is thought to be caused by coronary artery spasm. The procedure is conducted during coronary angiography.

  • The artery-narrowing drug ergonovine (or, alternatively, acetylcholine) is injected to provoke coronary artery spasm.
  • The person's response to the ergonovine is then measured.
  • If the individual experiences severe arterial spasm in response to ergonovine, he or she probably has variant angina.

Blood tests

The physician will order blood tests that gauge the amount of lipids (fatty substances) within the blood. High blood lipid can be a risk factor for coronary artery disease, which, in turn, increases the risk of angina.

The tests will create a "lipid profile" by measuring blood levels of

  • high-density lipoproteins (HDL; "good cholesterol")
  • low-density lipoproteins (LDL; "bad cholesterol")
  • triglycerides
  • other lipid markers

Recent research has shown that a blood test that measures the level ofC-reactive protein in the blood may be predictive of the mortality from heart disease. Other studies are also showing that the resting ESR (the "sedimentation rate" - how quickly the red blood cells settle to the bottom in a test tube) also has some predictive value about the mortality of heart disease.

 
 

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.