Introduction:

Myocardial infarction (MI) is a medical emergency that occurs when there is a sudden blockage of blood flow to the heart muscle, leading to damage or death of the heart tissue. MI is also known as a heart attack and is a leading cause of death worldwide. The diagnosis of MI is based on clinical symptoms, electrocardiogram (ECG) changes, and the presence of specific enzyme markers in the blood.

Enzyme Markers:

Enzyme markers are proteins that are released into the bloodstream when there is damage to the heart muscle. The most commonly used enzyme markers for the diagnosis of MI are creatine kinase (CK), CK-MB, and troponin.

1. Creatine Kinase (CK):

CK is an enzyme that is found in high concentrations in the heart, brain, and skeletal muscles. When there is damage to these tissues, CK is released into the bloodstream. CK has three isoforms: CK-MM (skeletal muscle), CK-MB (heart muscle), and CK-BB (brain tissue). CK-MB is the isoform that is specific to the heart muscle.

The normal range of CK in the blood is 30-200 U/L. In MI, the CK levels start to rise within 4-6 hours of the onset of symptoms, peak at 24 hours, and return to normal within 2-3 days. The elevation of CK-MB levels is more specific to MI than total CK levels.

1. CK-MB:

CK-MB is a subtype of CK that is found in high concentrations in the heart muscle. CK-MB levels start to rise within 4-6 hours of the onset of symptoms, peak at 12-24 hours, and return to normal within 2-3 days. The ratio of CK-MB to total CK is used to differentiate between MI and other causes of elevated CK levels.

The normal range of CK-MB in the blood is less than 5% of the total CK level. In MI, the CK-MB levels can increase up to 100 times the normal range.

1. Troponin:

Troponin is a protein that is found in high concentrations in the heart muscle. Troponin is released into the bloodstream when there is damage to the heart muscle. Troponin has three subtypes: troponin I (cTnI), troponin T (cTnT), and troponin C (cTnC). cTnI and cTnT are the subtypes that are used as enzyme markers for MI.

The normal range of cTnI and cTnT in the blood is less than 0.03 ng/mL and less than 0.1 ng/mL, respectively. In MI, the cTnI and cTnT levels start to rise within 3-4 hours of the onset of symptoms, peak at 12-24 hours, and can remain elevated for up to 10-14 days.

Conclusion:

Enzyme markers are important tools for the diagnosis of MI. CK, CK-MB, and troponin are the most commonly used enzyme markers for MI. The elevation of these enzyme markers in the blood is indicative of damage to the heart muscle. The timing and pattern of the elevation of these enzyme markers can help in the diagnosis and management of MI.