The goal of testing for angina is to distinguish between:
- Chest pain that is not heart-related, such as that due to skeletal muscle injury
- Chest pain that is due to treatable angina and not heart damage
- Chest pain that is due to a heart attack
When someone presents to the emergency room with an acute coronary syndrome – a group of symptoms that suggest heart injury – they are evaluated with a variety of laboratory and non-laboratory tests. These are used to determine the cause of the pain and the severity of the condition. Since some treatments for a heart attack must be given within a short period of time to minimize heart damage, an accurate diagnosis must be quickly confirmed.
Cardiac biomarkers, proteins that are released when muscle cells are damaged, are ordered to help differentiate angina from a heart attack. These include:
- Troponin – the most commonly ordered and cardiac-specific of the markers. Blood levels of troponin will be elevated within a few hours of heart damage and remain elevated for up to two weeks. Troponin tests are usually ordered initially in the ER when a person presents with symptoms of unstable angina and then a few more times in the next several hours to look at changes in concentrations. If the levels are normal, then it is much less likely that the symptoms and chest pain are due to heart muscle damage and more likely that the pain is due to stable angina. A rise and/or fall in the series of troponin results indicates a heart attack.
- A test called high-sensitivity troponin detects the same protein that the standard test does, just at much lower levels. Because this version of the test is more sensitive, it becomes positive sooner and may help detect heart injury and acute coronary syndrome earlier than the standard test. The hs-troponin test may also be positive in people with stable angina and even in people with no symptoms. When it is elevated in these individuals, it indicates an increased risk of future heart events, such as heart attacks. Currently, this test is not approved in the U.S., but research is ongoing and it may become available in the near future. It is already routinely used as a cardiac biomarker in clinical practice in Europe, Canada, and other countries as well.
- CK-MB – one particular form of the enzyme creatine kinase that is found mostly in heart muscle and rises when there is damage to the heart muscle cells; this test is used less frequently now.
Other tests that may be performed include:
- Myoglobin – a protein released into the blood when heart or other skeletal muscle is injured; this test is used less frequently now.
- BNP or NT-proBNP – released by the body as a natural response to heart failure; increased levels of BNP, while not diagnostic for a heart attack, indicate an increased risk of cardiac problems in persons with acute coronary syndrome.
Other more general screening tests may also be ordered to help evaluate the person's major body organs, electrolyte balance, blood glucose, and red and white blood cells to see whether there are any excesses, deficiencies, or dysfunctions that may be causing or worsening the person's symptoms. These include:
- Comprehensive Metabolic Panel – a group of usually 14 tests that is used as a broad screening tool to assess the current status of an individual's kidneys, liver, electrolyte and acid/base balance, blood glucose, and blood proteins.
- Complete Blood Count – a test used to screen for a variety of disorders that can affect blood cells, such as anemia and infection.
A range of non-laboratory evaluations and tests may be used to assess chest pain and other symptoms. These include:
- A medical history, including an evaluation of risk factors such as age, coronary artery disease (CAD), diabetes, and smoking
- A physical examination
- An electrocardiogram (ECG or EKG) – a test that looks at the heart's electrical activity and rhythm
- Continuous ECG monitoring – a person wears a monitor that evaluates heart rhythm over a period of time
Based on the findings of these tests, other procedures may be necessary, including:
- An exercise stress test
- Chest X-ray
- Coronary calcium scan – special X-ray exam that detects calcium in the coronary vessels, a sign of significant plaque development
- Radionuclide imaging – a radioactive compound is injected into the blood to evaluate blood flow and show images of narrowed blood vessels around the heart.
- Echocardiography – ultrasound imaging of the heart
- Cardiac catheterization – in this procedure, a thin flexible tube is inserted into an artery in the leg and threaded up to the coronary arteries to evaluate blood flow and pressure in the heart and the status of the arteries in the heart.
- Coronary angiography – X-rays of arteries using a radiopaque dye to help diagnose CAD; this procedure is performed during cardiac catheterization.
For more information on these, visit the National Heart, Lung and Blood Institute: How is a Angina Diagnosed?