Heart Attack Test/Troponin

Question 1. What is Heart Attack?

Heart Attack refers to death of parts of heart muscle due to lack of blood supply .This occurs when clots suddenly blocks of its main blood supply vessel (coronary artery) that is already partially narrowed by deposits of cholesterol plugs developed over many years. Heart is a very important organ constantly working to pump blood throughout our body at a rate of 60-80 beats per minute. Death from large heart attack occurs immediately when the heart as a pump fails as it’s starved of its own blood supply unless problem is identified and treated early.

Hence, early diagnosis is important to save life. Anyone with a sudden chest pain or tightness classically radiating up the neck and left arm and associated with breathlessness, nausea or sweating should seek immediate help for heart attack screen by doctor and appropriate ECG and blood testing. REMEMBER –DEATH OCCURS IF HEART ATTACK IS NOT TREATED WITHIN 1 HOUR.

Heart muscle is very unique and do not resemble other muscles of our body. When the muscle dies, bits of its muscle tissue damaged are released into circulation. These include CK, AST, LD and Troponins but CK and troponin are the only markers used to diagnose heart attack. Troponin is more specific and is now becoming the predominant marker for diagnosis of heart attack.

Question 2. How is troponin used?

Troponin tests are primarily ordered for people who have chest pain to see if they have had a heart attack or other damage to their heart. Either a Troponin I or a Troponin T test can be performed; usually a laboratory will offer one test or the other. Troponin is the latest blood test for diagnosing heart attack replacing older tests such as AST, LDH, CK–MB or myoglobin. It is preferred tests for a suspected heart attack because it is more specific for heart injury than other tests (which may become positive in non-heart muscle or skeletal muscle injury) and remain elevated for a longer period of time.

The Troponin test is used to help diagnose a heart attack, to detect and evaluate mild to severe heart injury, and to distinguish chest pain that may be due to other causes. In patients who experience heart-related chest pain, discomfort, or other symptoms and do not seek medical attention for a day or more, the Troponin test will still be positive if the symptoms are due to heart damage.

Question 3. When is it ordered?

The Troponin test will usually be ordered on a blood sample when a patient with a suspected heart attack first comes into the emergency room. It is sometimes ordered along with other tests such as CK, CK–MB, or myoglobin but these tests are now obsolete and do not offer any advantage. Typically, 2 or 3 Troponin tests are done over a 12- to 16-hour period.

In patients with stable angina, a Troponin test may be ordered if the patient’s symptoms get worse, occur when the patient is at rest, and/or no longer ease with treatment. These are all signs that the angina is becoming unstable, which increase the risk of a heart attack or other serious heart problem in the near future.

Question 4. What does the test result mean?

Normally, cardiac Troponin levels are so low that they cannot be measured. Even slight elevations may indicate some degree of damage to the heart. When a patient has significantly elevated Troponin concentrations, then it is likely that the patient has had a heart attack or some other form of damage to the heart. When a patient with chest pain and/or known stable angina has normal Troponin values, then it is likely that their heart has not been injured.

Question 5. I had an injection, will this affect my result?

Troponin test is not affected by damage to other muscles, so injections, accidents, strenuous exercise, and drugs that can damage skeletal muscle do not affect Troponin levels.

Question 6. I had chest pain few days back. Can Troponin be useful?

Troponin is useful in this case as it remains high for 1–2 weeks after a heart attack. Other heart markers would have returned to normal and would miss the diagnosis.

Question 7. Can Troponin be normal even if I have a heart attack?

Troponin measurement is used by your doctor along with physical exam findings, clinical history, and ECG to diagnose heart attack. Troponin levels may be normal within first 4-6 hours of heart attack.

Question 8. Can you have false positive Troponin result?

Any elevated troponin comes from the heart muscle. Hence, any condition causing muscle damage can cause elevations of troponin not related to heart attack such as heart muscle inflammation (myocarditis) and heart failure (CHF). Reports of false elevations of troponin in kidney diseases in the past are no longer true with current refined assay methods.

Question 9. Why bother another test as my doctor can do ECG to diagnose my chest pain?

Well, as is the case with many other medical tests, ECG nor troponin alone can correctly pickup all cases of heart attacks. However, when combined the chance of making a correct diagnosis and early treatment is better. Troponin assay is easy to do, does not require complex /expensive machine and can be readily done at bedside from a small blood sample. Unlike ECG, troponin result can be performed in smaller clinics using rapid kit or card tests without the need for specialised equipment and the visible colour change is read easily by any health worker.

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