Summary

• This test measures the level of a protein called troponin in your blood.
• Troponin testing, together with an electrocardiogram (ECG), helps doctors in the hospital emergency department find out whether you have had a heart attack or unstable angina (chest pain caused by reduced blood flow to the heart).
• Troponin is normally found inside heart muscle cells, where it helps the heart pump blood. If the heart muscle is damaged, troponin leaks into the bloodstream.
• Measuring the amount of troponin in your blood helps doctors assess whether your heart has been damaged and how serious the damage may be.
• The test is usually done when you arrive at the emergency department and repeated to see if the level is rising or falling.
• High-sensitivity troponin tests can detect very small amounts of troponin, allowing doctors to diagnose or rule out a heart attack quickly.
  

What are troponins?

Your heart is a muscle that pumps blood throughout your body. Your blood carries oxygen to your tissues and organs. For your heart to function properly, it must have a continuous supply of blood. In a heart attack (myocardial infarction), one of the arteries supplying blood to your heart becomes blocked. This means that blood flow is reduced or stopped entirely, the heart muscle cells are starved of oxygen, and they start to die. The longer the blockage is left untreated the more damage occurs.

Troponins are proteins found in your heart muscle cells – they help the muscle contract. If heart muscle cells are damaged or die, such as from a heart attack or angina, they release troponins into the bloodstream. The greater the injury, the more troponin is released.

There are three different troponins: troponin C, troponin I and troponin T. Troponin I and troponin T are used as blood tests because they are more specific to heart muscle whereas troponin C is not. Troponin C from the heart is the same as troponin C from skeletal muscles, so blood tests cannot tell where it came from. This means troponin C is not useful for detecting heart muscle damage because it can also be released after muscle injury or strenuous exercise.

Artery blockage and dying heart muscle.

Why get tested?

Acute chest pain is a relatively common emergency department presentation, yet only a minority of people will be diagnosed with an acute coronary syndrome (ACS). The troponin test has become one of the most valuable tools for emergency doctors because it helps identify or rule out a heart attack very quickly. Often doctors can confidently rule out a heart attack within 1–3 hours of arrival.

High sensitivity troponin tests are conducted by emergency departments to:

• Assess people with chest pain or suspected acute coronary syndrome (ACS)
• Identify or rule out a heart attack (myocardial infarction)
• Estimate the extent of heart muscle injury
• Help predict the risk of future heart problems

Normally, troponin levels are very low in healthy people. Any rise can indicate some heart damage. They go up dramatically if you have a heart attack. The more damage there is, the greater the concentration of troponin in the blood.

Most hospital labs use either troponin I or troponin T tests but not usually both. Both tests are considered comparably sensitive and specific for heart injury although troponin T levels can be higher in someone with kidney disease.

Even very small amounts of damage can now be detected because high-sensitivity troponin tests have been developed that are extremely accurate.

Having the test

Sample

Blood.

Preparation?
None.

Your results

Troponin levels usually rise within three or four hours of a heart attack, and then they start to fall back again. They can stay higher than normal for 10 to 14 days.

When you arrive at a hospital ED your vital signs - blood pressure, heart rate, respiratory rate and peripheral oxygen saturation- will be recorded and an ECG performed. If a diagnosis of ACS is considered likely, troponin testing will be done.

Assessing a person’s relative risk for heart attack is the key initial goal, rather than achieving a conclusive diagnosis, which may not always be possible straight away.

Troponin tests are repeated to see whether they are rising, falling, or remain flat. The rise or fall in troponin levels is important in working out whether you have had a heart attack or whether it is due to another heart problem. If you have a big rise in troponin levels, then it is highly likely that you’ve had a heart attack or some other form of heart damage.

Some people have higher troponin levels, and their levels don’t change. This is sometimes seen in heart problems such as myocarditis (inflammation of the heart muscle), weakening of the heart (cardiomyopathy), or congestive heart failure, chronic heart failure, high blood pressure (hypertension), kidney disease and some chronic inflammatory conditions that affect the heart.

This means that while a high troponin level can show there has been damage to the heart muscle, it does not always mean you have had a heart attack because troponin levels can also increase in other conditions that stress the heart. Your results must be interpreted together with your symptoms, a physical examination and ECG findings, and in the context of whether the troponin level rises or falls over time.

Rapid testing pathways
Australian emergency departments use high-sensitivity troponin tests with rapid testing pathways. A rapid testing pathway is a step-by-step process that uses the results of blood tests taken over a short period of time to quickly rule out or diagnose a heart attack.

• Hospitals use the 0/1-hour and 0/2-hour pathways.
• 0 hours means the time the first troponin blood test is taken when you arrive at the emergency department.
• 1 hour or 2 hours means a second blood sample is taken one or two hours later.

A significant rise or fall in high-sensitivity troponin between your first and repeat blood test is the key marker doctors look for because it shows a new heart injury has occurred. What counts as significant change in troponin (the delta change) depends on the specific test your pathology lab uses.

Understanding troponin results and cut-off limits
Troponin test results are not standardised. Different hospitals use different instrumentation. The instrument manufacturer sets the troponin levels and the changes over time that are most useful for assessing possible heart damage. These set levels are called clinical decision limits or cut-offs. The cut-off levels are specific to the test being used and are set by the test manufacturer.

Gender differences
Cut off levels are different for men and women. Men generally have slightly higher troponin levels than women. For this reason, there are different upper limits set for men and women when interpreting results.

The 99th percentile
You may be told that your diagnosis is based on the 99th percentile. The 99th percentile is the troponin level used as the upper limit of the normal range. It is based on testing a large group of healthy people. A result at or below this level is considered normal for 99 out of every 100 healthy people. Only about 1 in 100 healthy people will have a troponin level above this value. A troponin level above the 99th percentile suggests there may be heart muscle injury.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

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