The enzyme immediately raised following an MI is:

AIIMS Delhi NO-2016

Medical & Surgical Nursing

Easy

Appeared in: AIIMS Delhi NO-2016

Explanation

Myoglobin is a small protein found in heart and skeletal muscle, which is released rapidly into the blood after muscle injury.
Its levels begin to rise within 1 to 4 hours after the onset of a myocardial infarction, making it the earliest detectable serum cardiac marker.
While it is the first to rise, its main limitation is its low specificity, as it can also be elevated due to skeletal muscle injury.
A negative myoglobin test in the early hours after symptom onset is useful for ruling out an MI.

Option A: Troponin levels begin to rise later than myoglobin, typically 3-4 hours after the onset of myocardial injury.
Option C: The CK-MB isoenzyme rises later than myoglobin, with levels starting to increase 4-6 hours after an MI.
Option D: Haemoglobin is the oxygen-carrying protein in red blood cells and has no role as a biomarker for myocardial muscle damage.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Timeline of cardiac biomarker elevation after Myocardial Infarction (MI) as background academic context rather than a clinical decision trigger.
In the emergency department, the timing of symptom onset is critical for selecting and interpreting cardiac biomarker tests. Myoglobin's early rise can aid in rapid triage.
While myoglobin is the earliest marker, its low specificity means a positive result must be confirmed with a more specific marker like troponin. A diagnosis of MI is not made on myoglobin alone.
Nursing responsibility includes ensuring serial blood samples for cardiac markers are drawn at the correct time intervals as per hospital protocol to accurately track the trend (rise and fall).

How to Approach the Question

Identify the keyword in the question: The keyword is 'immediately', which asks for the very first enzyme/marker to rise after an MI.
Recall the common cardiac markers: The options include Myoglobin, Troponin, and CK-MB, which are all related to MI, and Haemoglobin, which is not.
Eliminate the outlier: Haemoglobin is involved in oxygen transport, not muscle damage. It can be safely eliminated.
Compare the onset times of the remaining markers: Remember the sequence of release. Myoglobin is a small protein and is released fastest (1-4 hours). Troponin follows (3-4 hours), and CK-MB is slightly later (4-6 hours).
Match the earliest onset with the question: Since Myoglobin has the earliest onset of rise, it is the correct answer for the marker that is 'immediately' raised.

Concept Tested & Keywords

Concept Tested: Timeline of cardiac biomarker elevation after Myocardial Infarction (MI)
Stem keywords: enzyme, immediately raised, MI, Myocardial Infarction
Lead-in keywords: immediately
Negative lead-in flag: false

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