ECG changes in myocardial infarction is?

Appeared in: WCL Staff Nurse - 2019

Explanation

ST-segment elevation is the characteristic ECG finding in an ST-elevation myocardial infarction (STEMI).
This elevation signifies a 'current of injury' resulting from acute transmural ischemia, which means the entire thickness of the heart wall is deprived of oxygen.
According to guidelines, ST elevation in two or more contiguous leads is a primary criterion for diagnosing STEMI.
Its presence is a critical indicator for immediate reperfusion therapy (e.g., percutaneous coronary intervention or fibrinolysis) to restore blood flow and save heart muscle.

Why Other Options Were Wrong

Option B: A wide QRS complex (greater than 120 milliseconds) is not a primary diagnostic sign of acute MI. It reflects a delay in ventricular depolarization.
Option C: The presence of a U wave is not associated with myocardial infarction.
Option D: A prolonged PR interval indicates a delay in conduction from the atria to the ventricles, not acute myocardial injury.

Related Visual

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain ECG Interpretation for Acute Myocardial Infarction as background academic context rather than a clinical decision trigger.
A nurse's ability to rapidly identify ST-segment elevation on a 12-lead ECG is a critical, life-saving skill. It triggers the activation of emergency protocols for reperfusion.
The principle 'time is muscle' underscores the urgency; delays in identifying STEMI and initiating treatment lead to more extensive and irreversible damage to the heart muscle.
Nursing responsibilities include obtaining an ECG within 10 minutes of arrival for a patient with chest pain, administering medications like aspirin, and preparing the patient for intervention.

How to Approach the Question

This is a factual recall question asking for a key diagnostic feature.
First, identify the core concept: ECG changes associated with Myocardial Infarction (MI).
Systematically review the classic ECG findings for an acute MI. The most critical and time-sensitive finding is ST-segment elevation, which defines a STEMI.
Evaluate each option. ST-segment elevation directly points to acute, full-thickness myocardial injury.
Analyze the distractors. Recognize that a wide QRS relates to conduction blocks, U waves relate to electrolyte imbalances (hypokalemia), and a prolonged PR interval relates to AV blocks. While these can sometimes co-exist or be complications of an MI, they are not the primary diagnostic hallmark of acute injury.

Concept Tested & Keywords

Concept Tested: ECG Interpretation for Acute Myocardial Infarction
Stem keywords: ECG changes, myocardial infarction
Lead-in keywords: is

Question ID

Qyv7k9B6ROx-43ki2QSVEP

Reference Book

E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) p. 7320-7322

E6 Medicine Harrison 22e Part 1 p. 1913-1915

E6 Physiology Ganong 27e Vol 2 Part 1 p. 81-83

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