Troponin

What is being tested?
This test measures the concentration of cardiac troponin in the blood. Troponin is a family of proteins found in skeletal and heart muscle fibres; it helps muscles contract. There are three forms of troponin: C, I and T. Cardiac troponin I and T are sufficiently different from those in skeletal muscle to be tested for specifically. These forms of troponin are normally present at low levels in the blood. When heart muscle cells are damaged, troponins are released into the circulation. The greater the damage, the higher the concentration of troponins in the circulation.
When a patient has a heart attack, troponin levels rise about 3 to 4 hours after the event and stay raised for 10 to 14 days.

How is the sample collected for testing?
A blood sample taken from a vein in the arm.

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
It is prescribed mainly for people with chest pain or a heart attack or other damage to the heart muscle. Either form of troponin can be tested; the laboratory usually measures one or the other. Troponin may be prescribed on its own or together with other markers of heart damage, such as CK, CK-MB and myoglobin. Troponin I and T have begun to replace CK and CK-MB because they are more specific for heart damage (compared with skeletal muscle damage) and stay raised for longer, but many doctors still prefer the extra information obtained by testing several markers.
Troponin is usually requested when a patient first arrives at hospital and is repeated at 6 and 12 hours. Troponin is used to diagnose a heart attack, to detect and assess mild to severe damage to the heart muscle, and to distinguish between the different causes of chest pain. In patients whose treatment has been delayed and who have had chest pain that may be due to a heart attack, with a feeling of pressure or other symptoms such as sweating, pain spreading to the arm, shoulders, jaw or neck, nausea or light-headedness for more than a day, troponin is the test of choice. This is because its concentration stays raised for a long time.

When is it requested?
Troponin is usually prescribed, together with other markers of heart damage such as CK, CK-MB or myoglobin, when a patient reports prolonged chest pain or other symptoms that may be due to heart damage. The test is usually carried out 2 or 3 times over 12-16 hours. In patients with stable angina (predictable episodes of chest pain due to inadequate blood supply to the heart muscle that are relieved by rest or appropriate medication), troponin may be prescribed if the symptoms get worse, occur at rest or soon after taking medication; this means that the angina is becoming unstable, putting the patient at a higher risk of heart attack.

What does the test result mean?
Normally, blood troponin levels are very low; sometimes a rise may indicate some kind of heart damage. When a patient has significantly raised troponin levels and other clinical signs, such as an abnormal ECG (electrocardiogram, which assesses heart rhythm), the patient is probably having a heart attack. If CK, CK-MB and myoglobin are normal but troponin is raised, there has probably been minor damage, or the event happened more than 24 hours earlier. If the first troponin test is normal but the following ones (6 and 12 hours later) are raised, the event probably happened about two hours before the first test, so troponin had not yet had time to rise. When CK is raised but CK-MB (more specific for the heart) and troponin are normal, the symptoms are probably due to another cause. When a patient with chest pain or stable angina has normal troponin, CK and CK-MB levels, there is probably no ongoing damage to the heart.
Troponin stays high for about 1-2 weeks after a heart attack. It is not usually affected by other muscle damage, such as intramuscular injections, accidents, strenuous exercise or medicines that damage muscle.

Is there anything else I should know?
Raised troponin levels are not enough on their own to diagnose a heart attack. A physical examination, the medical history and the ECG are equally important. Some people having a heart attack have normal troponin levels, and conversely some people with high troponin show no evidence of a heart attack. Troponin may be raised in some chronic conditions, such as myocarditis (inflammation of the heart muscle), congestive heart failure, severe infection, kidney disease, dermatomyositis or polymyositis.

1. What is a heart attack?
2. If I have chest pain, does it mean I am having a heart attack?
3. What other tests are specific for a heart attack?
4. What should I do if I am not sure whether I am having a heart attack?

1. What is a heart attack?
A heart attack means that part of the heart muscle tissue has died. The medical term for this is myocardial infarction. A heart attack usually begins with a feeling of heaviness or pain in the chest, which then spreads to the neck and left arm. There may be difficulty breathing, or exhaustion with a cold sweat.
A heart attack usually happens when one of the vessels that carry blood to the heart (the coronary arteries) is blocked. Partial blockage of these vessels is a result of atherosclerosis (known as hardening of the arteries). This blockage builds up gradually over the years as fatty plaques are deposited on the vessel wall. These plaques narrow and stiffen the artery and can break off unexpectedly, completely blocking the vessel.

2. If I have chest pain, does it mean I am having a heart attack?
Many problems can cause chest pain, and it is not possible to tell from the type of pain whether or not it is caused by a heart attack. Many people have chest pain because of a pulled muscle, emotional stress or lung problems. Pain that occurs during exercise, heavy work or periods of stress, lasts a few minutes and goes away with rest is often caused by angina. A rare type of chest pain is caused by spasm of the coronary arteries and is called variant angina. This spasm usually occurs at night while the patient is at rest and can cause severe but temporary pain.
If the pain lasts more than a few minutes, especially at rest, seek medical attention immediately.

3. What other tests are specific for a heart attack?
Several tests are usually used to determine whether a heart attack is taking place. Troponin detects damage to the heart muscle even when there is no other evidence of it. Myoglobin and CK, two other proteins found in muscle cells, do not rise with temporary chest pain. CK does not rise if the damage is minor. In patients having a heart attack, these markers of heart muscle damage rise and then fall over a period of 12 to 48 hours.

4. What should I do if I am not sure whether I am having a heart attack?
If you have prolonged chest pain, especially if it does not go away with rest – or if you have been diagnosed with angina and the pain does not go away despite treatment – seek medical attention immediately. Many patients having a heart attack die without even trying to call an ambulance or get to A&E.