What Enzymes Are Used in Diagnosing Acute Myocardial Infarction

There are several enzymes used in the clinical diagnosis of myocardial infarction, including myoglobin, cardiac troponin, creatine kinase, and creatine kinase-MB (CK-MB). Currently, the most commonly used biomarkers for detecting heart attacks are cardiac troponin and CK-MB. Troponin is a structural protein found in heart muscle cells and is released into the bloodstream when these cells are damaged or die. Typically, troponin levels begin to rise within 3–4 hours after a heart attack occurs.

Types of Cardiac Troponin

There are two main types of cardiac troponin: troponin I and troponin T. Both are used in diagnosing acute myocardial infarction, although they differ in how long they remain detectable in the bloodstream. Troponin I can be detected for up to 7–10 days following a heart attack, while troponin T may remain elevated for up to 10–14 days. The high specificity of troponin for heart muscle damage makes it a valuable diagnostic tool. When levels rise above a certain threshold, it strongly indicates myocardial injury, and combined with clinical findings, can confirm a diagnosis of heart attack.

Importance of Combining with ECG Findings

It is essential to interpret elevated troponin levels in conjunction with electrocardiogram (ECG) results. This combination helps determine whether the heart attack is ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), or another variant. This distinction is crucial for guiding treatment decisions and assessing the severity of the condition.

The Role of CK-MB in Diagnosis

Another important enzyme used in the diagnosis of acute myocardial infarction is CK-MB, a subtype of creatine kinase. Like troponin, CK-MB levels begin to rise in the blood approximately 3–4 hours after heart muscle damage occurs. A significant elevation—typically more than twice the normal level—can help confirm a diagnosis of heart attack. As with troponin, interpreting CK-MB results alongside ECG changes is vital for accurate classification of the type of myocardial infarction, particularly in distinguishing STEMI from NSTEMI.