The client went to the emergency room with a sudden onset of chest pain and difficulty of breathing. Which of the following results is indicative that the client is experiencing a myocardial infarction?
A. Myoglobin level of 98 mcg/L.
B. Troponin T of 0.09 ng/mL.
C. Troponin I 0.5 ng/mL.
D. Creatine kinase (CK-MB) 155 units/L.
Correct Answer: A. Myoglobin level of 98 mcg/L.
The normal value of myoglobin is lower than 90 mcg/L; An elevation could indicate a myocardial infarction. Myoglobin, an oxygen-carrying protein found in cardiac muscle and striated skeletal muscle, presents an attractive alternative to CPK and LDH in the emergency department setting for identification of acute myocardial infarction. Myoglobin levels may be elevated in the serum within one hour after myocardial cell death with peak levels reached within four to six hours.
Option B: The troponin T level is normal. Cardiac troponin T is measured in nanograms per milliliter (ng/mL). If the client’s troponin T level is above the 99th percentile for the test being used, the doctor will likely diagnose a heart attack. Levels that start high and fall suggest a recent injury to the heart. It could be a mild heart attack.
Option C: The troponin I level is normal. High levels of troponin are an immediate red flag. The higher the number, the more troponin — specifically troponin T and I — has been released into the bloodstream, and the higher the likelihood of heart damage. Troponin levels can elevate within 3-4 hours after the heart has been damaged and can remain high for up to 14 days.
Option D: Creatine kinase level has a normal value. The ECG and the determination of serum enzymes creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) may be falsely normal early in acute myocardial infarction.