Which laboratory investigation is essential for a patient admitted in emergency with severe angina and ST ele… - Daman & Diu Staff Nurse - 2018

Daman & Diu Staff Nurse - 2018

Medical Surgical Nursing

Easy

Appeared in: Daman & Diu Staff Nurse - 2018

Explanation

Troponin (specifically cardiac Troponin I and T) is the preferred and most specific biomarker for diagnosing myocardial infarction (MI).
These proteins are released exclusively from damaged heart muscle, making them highly specific for cardiac injury.
Troponin levels rise within 3-6 hours of injury, peak at 12-24 hours, and remain elevated for 7-14 days, providing a wide window for diagnosis.
High-sensitivity troponin assays are the current gold standard, allowing for the detection of even minor myocardial necrosis.

Option A: Creatine kinase (CK-MB) is less specific to cardiac muscle than troponin and can be elevated in cases of skeletal muscle injury. It is no longer the primary diagnostic marker.
Option C: Hemoglobin measures the blood's oxygen-carrying capacity. It does not diagnose heart muscle damage. A complete blood count (which includes hemoglobin) is a routine test but not the essential one for diagnosing MI.
Option D: Liver enzymes (like ALT and AST) are markers for liver cell injury. They are not specific for cardiac damage and are not used to diagnose an MI.

Clinical Relevance

Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Cardiac Biomarkers in Myocardial Infarction Diagnosis in acute care settings.
A key nursing responsibility in the emergency department is the prompt collection of blood for cardiac biomarker analysis, but also understanding that definitive treatment for STEMI should not be delayed for the results.
Nurses must educate patients and families about the significance of serial blood draws for troponin, explaining that a trend (a rise in levels) is often more important than a single value for confirming the diagnosis.
What if? If the patient had chest pain but a NORMAL ECG (no ST elevation), the troponin level becomes even more critical. An elevated troponin in this case would lead to a diagnosis of a Non-ST-Elevation Myocardial Infarction (NSTEMI), which has a different immediate treatment pathway than STEMI.

How to Approach the Question

First, analyze the patient's presentation: 'severe angina' and 'ST elevation' are classic signs of a ST-Elevation Myocardial Infarction (STEMI).
The question asks for the 'essential' laboratory investigation. This means you need to identify the most important and definitive test for confirming heart muscle damage.
Recall the different types of cardiac biomarkers and their properties.
Compare the specificity and sensitivity of the options. Troponin is highly specific to heart muscle.
Creatine kinase (CK-MB) is a historical marker and less specific. Hemoglobin and liver enzymes are not primary diagnostic tests for MI.
Conclude that Troponin is the gold standard and therefore the essential investigation.

Concept Tested & Keywords

Concept Tested: Cardiac Biomarkers in Myocardial Infarction Diagnosis
Stem keywords: severe angina, ST elevation, laboratory investigation, emergency
Lead-in keywords: essential
Clinical cues: The combination of severe angina (chest pain) and ST elevation on an ECG is highly indicative of a ST-Elevation Myocardial Infarction (STEMI), a medical emergency.
Negative lead-in flag: false

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E6 textbook of Applied Biochemistry and Nutrition & DieteticsHarbans Lal (pp 26-464 of 479) p. 140-142

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 259-261

E6 Medicine Harrison 22e Part 2 p. 20-22