Hypertension & Coronary Artery Disease Q 40

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A client enters the ER complaining of chest pressure and severe epigastric distress. His VS are 158/90, 94, 24, and 99*F. The doctor orders cardiac enzymes. If the client were diagnosed with an MI, the nurse would expect which cardiac enzyme to rise within the next 3 to 8 hours?

  

     A. Creatine kinase (CK or CPK)

     B. Lactic dehydrogenase (LDH)

     C. LDH-1

     D. LDH-2

    

    

Correct Answer: A. Creatine kinase (CK or CPK)

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Creatine kinase (CK, formally known as CPK) rises in 3-8 hours if an MI is present. When the myocardium is damaged, CPK leaks out of the cell membranes and into the bloodstream. Creatine kinase activity is one of the oldest markers of acute myocardial infarction (AMI). Creatine kinase activity begins to rise within 12 hours of AMI symptoms, peaks at 24 to 36 hours, and normalizes after 48 to 72 hours.

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Option B: Lactic dehydrogenase rises in 24-48 hours. Lactate dehydrogenase is an enzyme that is present in almost all body tissues. Because LDH is non-specific and routine isozyme measurement is usually unavailable in clinical laboratories, LDH measurements provide incomplete information, and alternate assays such as CK for muscle, ALT for liver, troponin for heart diseases, etc. are needed.

Option C: Isozyme LDH-1 has four heart subunits (4H) and is the major isozyme present in the heart tissue. The assembly of the enzymes occurs in a defined ratio through a tissue-specific synthesis of subunits, hence providing tissue specificity, i.e., heart-specific LDH (LDH-1) preferentially synthesizes all four H subunits, while liver LDH (LDH-5) is exclusively made of all M-subunits. In acute myocardial infarction, LDH-1 isozyme remains elevated from the second day to up to the 4th day.

Option D: LDH-2 rises in 8-24 hours. Isozyme LDH-2 has three heart and one muscle subunit (3H1M) and is the major isozyme of the reticuloendothelial system and RBC. LDH can be used as a satisfactory marker for the staging of a disease (S-classification), monitor prognosis or response to treatment, and to evaluate body fluids other than blood. The decrease in LDH levels during treatment is indicative of a better prognosis and/or good response to treatment in conditions such as acute myocardial infarction or liver injury.

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