Troponin

Troponin tests are primarily ordered to help diagnose a heart attack and rule out other conditions with similar signs and symptoms. Either a troponin I or troponin T test can be performed; usually a laboratory will offer one test or the other. The concentrations are different, but they basically provide the same information.

Troponin I and troponin T are proteins found in heart muscle and are released into the blood when there is damage to the heart.

Troponin tests are also sometimes used to evaluate people for heart injury due to causes other than a heart attack or to distinguish signs and symptoms such as chest pain that may be due to other causes. Testing may also be done to evaluate people with angina if their signs and symptoms worsen.

Troponin tests are sometimes ordered along with other cardiac biomarkers, such as CK–MB or myoglobin. However, troponin is the preferred test for a suspected heart attack because it is more specific for heart injury than other tests (which may be elevated in the blood with skeletal muscle injury) and remain elevated for a longer period of time.

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.

A troponin test will usually be ordered when a person with a suspected heart attack first comes into the emergency room, followed by a series of troponin tests performed over several hours.

A heart attack may be suspected and testing done when a person has signs and symptoms such as those listed below. Note that not everyone will experience chest pain, and women are more likely than men to have sign and symptoms that are not typical.

• Chest pain, discomfort and/or pressure (most common)
• Rapid heart rate, skipping a beat
• Shortness of breath and/or difficulty breathing
• Fatigue
• Nausea, vomiting
• Cold sweat
• Lightheaded
• Undue fatigue
• Pain in other places: back, arm, jaw, neck, or stomach

In people with stable angina, a troponin test may be ordered when:

• Symptoms worsen
• Symptoms occur when a person is at rest
• Symptoms are no longer eased with treatment

These are all signs that the angina is becoming unstable, which increases the risk of a heart attack or other serious heart problem in the near future.

A high troponin and even slight elevations may indicate some degree of damage to the heart. When a person has significantly elevated troponin levels and, in particular, a rise in the results from a series of tests done over several hours, then it is likely that the person has had a heart attack or some other form of damage to the heart. Levels of troponin can become elevated in the blood within 3 or 4 hours after heart injury and may remain elevated for 10 to 14 days.

In people with angina, an elevated troponin may indicate that their condition is worsening and they are at increased risk of a heart attack.

Troponin levels may also be elevated with other heart conditions such as myocarditis (heart inflammation), weakening of the heart (cardiomyopathy), or congestive heart failure, and with conditions unrelated to the heart, such as severe infections and kidney disease.

Normal troponin values in a series of measurements over several hours means that it is unlikely that a person's heart has been injured. Signs and symptoms may be due to a cause unrelated to the heart.

Because troponin tests are measuring cardiac muscle-specific troponin, the test is not affected by damage to skeletal muscles, so injections, accidents, and drugs that can damage muscle do not affect cardiac troponin levels. Troponin may rise following strenuous exercise, although in the absence of signs and symptoms of heart disease, it is usually of no medical significance.

Increased troponin levels should not be used by themselves to diagnose or rule out a heart attack. A physical exam, clinical history, and ECG are also important. Your healthcare provider may also need to see whether the troponin levels from a series of tests are stably elevated or show a rise over several hours.

Very rarely, people who have a heart attack will have normal troponin concentrations, and some people with increased troponin concentrations have no apparent heart injury.