CKMB test in myocardial infarction

This is an automatically translated article.

The article was consulted with Master, Doctor Tran Hong Nhat - Interventional Cardiologist - Cardiovascular Center - Vinmec Central Park International General Hospital.
CKMB test is one of the biochemical tests for early diagnosis of acute myocardial infarction. Clinicians consider the CKMB index to have a relatively high specificity for the disease compared with many other plasma enzymes such as myoglobin. However, this test can still give a false-positive result in many cases.

1. What is Creatine Kinase (CK)?

Creatine Kinase, formerly Creatine Phosphokinase, is an intracellular enzyme that exists in large quantities in skeletal, cardiac, and cerebral muscle. A small amount of CK may be present in other visceral tissues. Currently, scientists have found 3 main isoenzymes of CK including:
CK - MM: skeletal muscle. CK - MB: heart muscle CK - BB: brain muscle. Creatine Kinase that exists in the myocardium usually has a CK-MB concentration that fluctuates above 40% and the remaining 60% is CK-MM. The vast majority of CK in plasma is the isoenzyme CK-MM.
Normally, Creatine Kinase exists at normal levels in the blood. When there is disruption of cell membranes due to hypoxia or other trauma, CK is released from the cytosol into the circulation. On this basis, serum CK concentrations are elevated.

2. Learn about the CKMB test in myocardial infarction

CKMB test is performed to measure the level of CK (Creatine Kinase) in a patient's blood, thereby making early diagnoses related to myocardial infarction.
As mentioned above, the main site of CK-MB is myocardium, whereas, normal serum of healthy people mainly contains CK-MM. Therefore, the use of a sensitive test method can detect markers of CK-MB and CK-BB in serum.
The release of CK-MB from the myocardium to the serum can come from any process that disrupts the sac membranes in the heart, such as myocarditis, cardiac trauma, cardiac surgery... Therefore , elevated serum CK-MB levels are a very characteristic sign of cardiac cell damage, but not specific to acute myocardial infarction.
For this reason, it is an exclusion test, not the only test to diagnose myocardial infarction.

3. Evolution of Creatine Kinase in Acute Myocardial Infarction

After the onset of symptoms of myocardial infarction, CK and CKMB will increase in serum within 3 to 6 hours, in some cases, this increase may persist for 16 to 30 hours. CK-MB usually disappears from serum at a faster rate than CK.
This also means that testing for CKMB needs to be done as soon as possible after the onset of symptoms and needs to be repeated several times during the first 48 hours. The highest CKMB levels were found to range between 15% and 30% of total CK levels.

4. How much CKMB index is normal?

When the CKMB test shows a reading below 24 U/I, this is normal and doctors can remove the cause of a heart attack from the list of suspicions.
However, if this CKMB index rises above 24 U/I, this sign does not mean that the patient has a myocardial infarction but can only be suspected. Patients need to conduct more tests to come to the most accurate conclusion.

5. Why is the CKMB test chosen as one of the special acute myocardial infarction tests?

The CKMB index is of particular value for myocardial infarction because of the following reasons:
Total creatine kinase has a sensitivity of up to 98% for early myocardial infarction (a few false positives). for other reasons). CK allows early diagnosis because CK levels are very high within 3 to 6 hours of symptom onset and can peak 24 to 36 hours after myocardial infarction. Compared with other plasma enzymes, CK can be 6 to 12 times higher than normal – a very recognizable sign. In particular, CKMB is present mainly in the myocardium, so most heart diseases that cause myocardial cell destruction cause CKMB to be elevated, reflecting the severity of the disease. CKMB may even allow the differential diagnosis between reversible infarcts and recurrent infarcts. The CKMB index is a gold standard in diagnosis from onset of symptoms within 24 hours.

6. Some causes of increased CKMB index other than myocardial infarction

Besides myocardial cell damage due to myocardial infarction, CKMB index can also increase due to many other causes such as:
Myocarditis . Heart injury. Congestive heart failure: at this time CKMB increases moderately. Coronary vasospasm: CKMB rises and returns to normal very quickly. Muscular dystrophy, polymyositis. Burn. Typhus ... In general, the CKMB test has more significance in early diagnosis of acute myocardial infarction than other plasma enzymes. However, this is not the only test for acute myocardial infarction as it still has a certain false-positive rate.
To protect heart health in general and detect early signs of heart attack and stroke. Currently, Vinmec International General Hospital has been and continues to deploy Cardiovascular Screening Package - Basic Cardiovascular Examination. The patient examination package detects cardiovascular problems at the earliest through tests and modern imaging methods. The package is for all ages, genders and is especially essential for people with risk factors for cardiovascular disease.
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Reference source: ncbi.nlm.nih.gov