Normal Values and Clinical Significance of Cardiac Enzyme Tests

Dec 01, 2022 Source: Cainiu Health

Dr. Tian Hongbo

Introduction

The laboratory test report for myocardial enzymes mainly includes lactate dehydrogenase, creatine kinase, and creatine kinase-MB. By comparing these values, it can be determined whether a patient has a disease. In addition to the above common tests, other indicators such as hydroxybutyrate dehydrogenase may also be evaluated. If any of these test results are abnormal, further cardiac ultrasound examination is required to confirm the presence of heart disease.

The blood tests for myocardial enzymes mainly include lactate dehydrogenase, creatine kinase, and creatine kinase isoenzyme. These values are compared to determine whether the patient has any underlying diseases.

1. Lactate Dehydrogenase (LDH)

The normal range for lactate dehydrogenase is 100 IU/L to 240 IU/L. LDH is widely distributed throughout the human body and may increase in conditions such as myocardial infarction, hepatitis, kidney disease, and malignant tumors.

2. Creatine Kinase (CK)

The normal range for creatine kinase is generally 24 IU/L to 194 IU/L. Abnormal levels may result from physiological factors such as intense physical activity, or could be due to myocardial injury or chronic kidney disease.

3. Creatine Kinase Isoenzyme (CK-MB)

The normal range for creatine kinase isoenzyme is 0 IU/L to 25 IU/L. The most important clinical significance of this test is in the diagnosis of acute myocardial infarction. CK-MB levels in serum begin to rise 4–6 hours after the onset of chest pain in acute myocardial infarction, peak within 12–36 hours, and return to normal within 72 hours.

In addition to these common tests, other measurements such as hydroxybutyrate dehydrogenase may also be evaluated. Patients with abnormal test results should undergo further evaluation with cardiac ultrasound to determine the presence of conditions such as coronary artery stenosis, cardiac dysfunction, or heart failure.

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Can a complete blood count (CBC) show whether cardiac enzymes are elevated?

Under normal circumstances, a routine blood test cannot determine whether cardiac enzymes are elevated. A routine blood test refers to an examination that assesses the status of blood and detects diseases by analyzing the quantity and morphological distribution of blood cells, including red blood cell count, hemoglobin, white blood cells, white blood cell differential count, and platelets. It typically does not include cardiac enzymes, and therefore cannot indicate whether cardiac enzyme levels are high or not.

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What type of tube is used for blood collection to test cardiac enzymes?

Blood collection for cardiac enzymes typically uses a yellow-top tube. Elevated cardiac enzymes primarily indicate acute myocardial infarction, in which myocardial cells suffer from ischemia and hypoxia, leading to the release of large amounts of cardiac enzymes into the bloodstream. An increase in cardiac enzymes suggests that myocardial cell necrosis has occurred. When elevated cardiac enzymes are accompanied by symptoms such as chest tightness, chest pain, or pressure-like pain, acute myocardial necrosis or acute myocardial infarction should be considered.

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Is elevated myocardial enzyme level serious?

Elevated myocardial enzymes can be serious, and the severity should be assessed based on the patient's clinical presentation and overall condition. In mild cases of myocarditis causing elevated myocardial enzymes, levels can return to normal with proper treatment. However, when the elevation is severe, it may impair cardiac function. Patients should prioritize adequate bed rest and consume nutritious foods to support recovery in daily life.

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What are the symptoms of abnormal cardiac enzymes?

Abnormal myocardial enzymes are mainly characterized by elevated levels, commonly seen in conditions such as myocardial infarction, viral myocarditis, and cirrhosis. Different underlying diseases produce varying symptoms. Common manifestations include chest pain, fever, nausea, and vomiting; severe cases may lead to arrhythmias, shock, or heart failure, as well as palpitations and shortness of breath. Other symptoms may include abdominal discomfort, fatigue, loss of appetite, nausea, and bloating.