Question

Of CPK and LDH which rises earliest?

a) CPK
b) LDH
c) Both simultaneously
d) Neither rises after MI

Answer 1

The enzyme CPK rises earliest after a myocardial infarction, making it the key marker for heart attack diagnosis. CPK levels increase significantly soon after an MI, whereas LDH levels peak later and remain elevated longer.

Step-by-step explanation:

The correct answer to which enzyme rises earliest after a myocardial infarction (MI) or heart attack is CPK (Creatine phosphokinase). CPK serves as a marker enzyme for the diagnosis of MI because it is the first enzyme to show elevated levels in the blood plasma shortly after a heart attack. Specifically, the CPK-MB isoenzyme is indicative of heart damage, and it maintains a higher concentration for 1-2 days after an MI. Notably, the concentration of CPK can rise to 10 times normal levels after a first attack, 100 times if another attack occurs within a short time, and up to 300 times after a third attack, which can be lethal. In contrast, the isoenzyme form of lactate dehydrogenase (LDH), particularly LDH₁, sees an increase during an MI, but it peaks later than CPK and can remain elevated for up to 6 days following an MI.