Doctors often conduct a troponin test – which measures the levels of troponin in your bloodstream – to help diagnose a heart attack, apart from electrocardiography (ECG) and an echocardiogram (ECHO). Troponin is considered a biomarker, as high levels of it can confirm a heart attack, say experts.
Dr Zakia Khan, senior consultant, interventional cardiology, Fortis Hospital, Mumbai, says troponin is a cardiac protein that is released into the bloodstream when the heart muscles get damaged due to severe stress resulting from a heart attack. “Whenever the troponin level is elevated, it means there is an injury to the myocardium [muscular tissue of the heart] or the myocardium is severely stressed,” she adds.
What is troponin?
Troponin is a protein present in heart muscles. Normally, it is also found in other tissues of the body. Dr Sreekanth B. Shetty, senior consultant and head, interventional cardiology, Sakra World Hospital, Bangalore, says it is a part of the mechanical system of the heart. “Troponin, along with actin and myosin, is responsible for muscle activation and contraction. It gets released into the blood when there is a muscle injury. The muscle injury could be due to inflammation, any trauma to the heart muscle or a block in the heart,” he explains.
Basically, there are three types of heart attacks: STEMI (ST-elevation myocardial infarction), NSTEMI (non-ST-elevation myocardial infarction) and unstable angina. Dr Sumanta Chatterjee, interventional cardiologist, AMRI Hospital, Dhakuria, Kolkata, says troponin levels become elevated during the first two types of heart attacks. “In unstable angina, it doesn’t rise. This form of heart attack is also associated with chest pain and mortality, but surprisingly, it does not raise the levels of troponin. It has a different pathophysiology,” he adds.
While diagnosing a cardiac injury, the levels of two types of troponin — troponin T and troponin I — are checked. Troponin I is more specific to the heart. The test is recommended when an acute coronary syndrome is suspected, says Dr Khan. It is used for both the prognosis and diagnosis of the condition. “We order this test in case of a casualty, an emergency or for a person who’s already admitted to the hospital when we suspect a heart attack. It’s an important test for what we call a cardiac trial. When anyone comes in with acute chest pain and we want to see if they have suffered a heart attack, we do this test along with a serial ECG,” she explains.
What level of troponin indicates a heart attack?
There are different kinds of troponin tests, say experts, and the cut-offs depend on the kind of test being performed. Dr Shetty says either a high-sensitivity troponin test (which can detect very small changes in troponin levels) or a standard troponin test is conducted. “For the high-sensitivity test that measures troponin I levels, 11 nanograms per liter is the upper limit. It is very useful in diagnosing heart attacks very early,” he adds.
There are also qualitative tests that use a strip, where a drop of blood is placed into its well. The reports are either positive or negative. “It doesn’t tell the level of troponin. Quantitative tests are important because they use the high-sensitivity method and check the elevation or reduction in levels of troponin with time,” says Dr Shetty.
It takes six hours for the troponin levels to elevate or show a positive result after a heart attack episode. Dr Chatterjee says more than 70 to 80 percent of people they see in the emergency ward arrive seven to eight hours after having a heart attack. Consequently, their troponin levels are high upon arrival. “At 24 hours, troponin rises to its peak levels and stays in the bloodstream for seven to 10 days. Fortunately, if one comes within the six hours, clinical judgment and an ECG can help diagnose it,” he explains.
If the troponin test shows a negative result, they are monitored for any new changes in the ECG, and the test is repeated after six hours. “If there are new changes in the ECG during monitoring or if the troponin levels are elevated when checked again after six hours, it would mean that the chest pain is because of a heart attack,” notes Dr Shetty.
Other causes of elevated troponin levels
All cases of troponin level elevation cannot be interpreted as a heart attack. Experts say there can be other cardiac and non-cardiac conditions that elevate troponin levels as well. So, it should be interpreted as per the person’s problem.
Dr Shetty says, “Stress cardiomyopathy also causes heart muscle injury because of intense emotional stress. So, it will look exactly like a heart attack in terms of ECG changes, echocardiographic findings and troponin elevation. But, in these cases, the next troponin test will show a downward trend instead of an increase.”
Some other conditions that can cause elevated troponin levels include:
- Heart failure
- Pulmonary embolism
- Atrial fibrillation
- Acute kidney injury
- Severe sepsis
- Extremely low blood pressure
Takeaways
- A troponin test measures the levels of troponin in your bloodstream. High levels of troponin can confirm a heart attack.
- Troponin is a cardiac protein that’s released into the bloodstream when there is a muscle injury resulting from a heart attack.
- Troponin levels increase six hours after a heart attack and remain in the blood for a week or two.
- An elevation in troponin levels cannot be interpreted as a heart attack in every case. Other conditions like heart failure, acute kidney injury and pulmonary embolism can also elevate troponin levels.
