Creatine kinase (CK)
- It’s an enzyme found primarily in the heart and skeletal muscles, and in smaller amounts in the brain. When the total CK level is substantially elevated, it usually indicates injury or stress to one or more of these areas.When a muscle is damaged, CK leaks into the bloodstream. Determining which isoenzyme (specific form of CK) is elevated will help determine which tissue has been damaged.
- CK can be measured as the total enzyme in the serum, or each of its three isoenzymes may be measured. The isoenzymes include:
CK1 (CPK-BB): produced primarily by brain tissue and smooth muscle of the lungs
CK2 (CPK-MB): produced primarily by heart tissue
CK3 (CPK-MM): produced primarily by skeletal muscle
CK, along with asparate aminotransferase (AST) and troponin, is assessed in the case of suspected myocardial infarction.
Troponin
- The troponins are proteins found in skeletal muscle and heart muscle. There are actually three types of troponin: C, I, and T. Subgroups of these, known as cardiac troponin I and cardiac troponin T, are specific to the heart muscle fibers. When there is damage to the heart muscle, the cardiac troponins are released into the blood. Thus, the two cardiac troponins are used to determine whether a person has had a myocardial infarction or some other injury to the heart muscle, such as when a cardiac contusion has occurred during chest trauma.
- Cardiac troponin is typically measured along with other cardiac biomarkers, such as CK, CK-MB, and myoglobin. Following heart muscle damage, Tropinin I will increase in 4 to 6 hours, peak in 12 to 20 hours, and return to normal in 3 to 10 days. Tropinin T will increase in 3 to 12 hours, peak in 12 to 24 hours, and return to normal in 10 to 15 days. When a patient with chest pain presents to the emergency department, the cardiac troponin is immediately evaluated. It is then repeated 2 to 3 times in the first 12 to 16 hours, usually at 6 and 12 hours. Both of the cardiac troponins do not need to be checked. Typically an institution will perform one or the other. It is important for health-care providers to use the troponin level as only one part of the clinical picture. The patient’s history, physical assessment, and other test results, including electrocardiogram (ECG), must all be taken into consideration.
Myoglobin
- It’s a heme-containing, oxygen-binding protein which is present in the cytoplasm of cardiac and skeletal muscle cells. It serves as a reservoir of oxygen to meet very short-term needs. When muscle cell injury occurs through disease, as in myocardial infarction, or through trauma, myoglobin is released into the blood. This usually begins within 2 to 4 hours following muscle tissue damage, peaks in 8 to 10 hours, and returns to a normal level in about 1 day.
- Myoglobin is excreted by the kidneys (myoglobinuria) and is detected in the urine up to 1 week following muscle tissue injury.
Cardiac Markers and time of elevation
References:
Manual of laboratory and diagnostic tests Frances Fischbach
