The cardiac biomarker that is preferred for diagnosis of Acute Myocardial Infarction is troponin, which may be either cardiac troponin T (cTnT) or cardiac troponin I (cTnI). Troponin (either cTnT or cTnI) is the preferred biomarker due to its superior sensitivity and accuracy. cTnT and cTnI are specific proteins found in cardiac muscle. They are not normally found in serum; they are released only when myocardial damage occurs. A third troponin, troponin C, is not useful as a cardiac biomarker as it is not specific for the heart.
Sample Requirement
Description
Sample Type
Blood ,Fasting not required
Sample Volume
1-2 milliliters (ml)
Collection Method
Venipuncture (blood drawn from a vein)
Anticoagulant
Ethylenediaminetetraacetic acid (EDTA) or plain serum seperator tube
Handling
Samples should be handled and transported carefully to prevent hemolysis (breakdown of red blood cells) and contamination. It is important to follow proper sample collection and handling protocols.
Storage
Samples should be stored at 2-8°C (refrigerated) if not immediately tested. Avoid freezing and thawing the samples repeatedly, as it may affect the stability of cardiac troponin.
Transport
Properly packaged and transported on ice or in a refrigerated container to maintain sample integrity during transit to the laboratory.
Troponins are a group of proteins that are essential for muscle contraction. They are found in both skeletal and cardiac muscle, but they have slightly different functions in each type of muscle.In skeletal muscle, troponins help to regulate the interaction between actin and myosin, which are the two main proteins involved in muscle contraction. Troponins do this by binding to calcium ions, which are released from the sarcoplasmic reticulum when a muscle fiber is stimulated. When calcium ions bind to troponin, it changes the shape of troponin, which in turn allows actin and myosin to interact and contract the muscle fiber.
There are three types of troponins: troponin C, troponin I, and troponin T. Each type of troponin has a different function.
Troponin C contains the binding sites for calcium ions.
Troponin I inhibits the interaction of myosin with actin.
Troponin T binds the troponin components to tropomyosin.
When muscle cells are damaged, troponins can leak into the bloodstream. This can be used as a marker for muscle damage, such as a heart attack.
Cardiac disorders that are associated with troponin (cTnT/cTnI) elevation include:
AMI
Unstable angina
Myocarditis
Heart failure (chronic or acute decompensated)
Pericarditis
Percutaneous coronary intervention without complications
Rhabdomyolysis with cardiac injury
Multi-organ failure
cTnI and cTnT will start to rise between 2 and 12 hours after a cardiac event, peaking at 18 to 24 hours. cTnI remains elevated 7 to 10 days, while cTnT stays in the circulation 10-14 days.
Both cTnI and cTnT are cardiac specific, rapidly released after injury, remain in circulation for several days, are normally in low concentration in serum or plasma, and both are available as point-of-care (POC) tests.
A troponin level that is higher than 99% of the levels found in a healthy population is one sign of an acute myocardial infarction (AMI). The exact cutoff value depends on the sensitivity of the test used. If a troponin level is high enough and there are other signs of ischemia, such as chest pain or an abnormal electrocardiogram (ECG), then a diagnosis of AMI can be made. Ischemia is a condition in which the heart does not get enough blood.
Some typical cutoff concentrations for troponin are:
cTnT <0.01 ng/mL: No detectable cardiac injury
cTnI < 0.03 ng/mL: No detectable cardiac injury,
Probable heart attack: above 0.40 ng/mL
cTnI and cTnT will start to rise between 2 and 12 hours after a cardiac event, peaking at 18 to 24 hours. cTnI remains elevated 7 to 10 days, while cTnT stays in the circulation 10-14 days.
other test for supporting Myocardial infarction – CpK-MB ,ECG
Cardiac troponins are proteins found in heart muscle cells (cardiomyocytes) that are released into the bloodstream when there is damage to the heart muscle.
Why are cardiac troponin tests performed?
Cardiac troponin tests are performed to assess heart damage, specifically myocardial injury or myocardial infarction (heart attack). They help diagnose and monitor heart-related conditions.
How is a cardiac troponin test conducted?
A cardiac troponin test involves drawing a blood sample from a vein, typically through venipuncture. The sample is then analyzed in a laboratory using specific assays to measure the levels of cardiac troponin.
What is the difference between troponin T and troponin I?
Troponin T (cTnT) and troponin I (cTnI) are different subtypes of cardiac troponins. Both are markers of heart muscle damage, but they have slightly different characteristics and different assays used for their measurement.
How long does it take for cardiac troponin levels to rise after a heart attack?
Cardiac troponin levels start to rise within a few hours after heart muscle damage occurs. They typically remain elevated for several days, and the peak level usually occurs within 24 to 48 hours after the onset of symptoms.
Can cardiac troponin levels be elevated for reasons other than a heart attack?
Yes, cardiac troponin levels can be elevated in conditions other than heart attacks. These may include unstable angina, congestive heart failure, myocarditis, pulmonary embolism, and other causes of heart muscle damage. Additionally, strenuous exercise or skeletal muscle injury can temporarily increase troponin levels.
What do different troponin levels indicate?
Elevated troponin levels above the normal range indicate heart muscle damage. The degree of elevation can provide information about the severity of the damage. Serial troponin measurements over time can help determine if the levels are increasing, decreasing, or stable, which aids in the diagnosis and management of heart-related conditions.
Are there any limitations or factors that can affect troponin test results?
Yes, there are some factors that can affect troponin test results. These include kidney disease, certain medications, age, and underlying health conditions. It’s important for healthcare providers to consider these factors when interpreting the test results.
