NORCET 3 - 2022 (Shif…: In treadmill test changes in ECG graph may?

NORCET 3 - 2022 (Shift-1)

Medical & Surgical Nursing

Easy

Appeared in: NORCET 3 - 2022 (Shift-1)

Explanation

A treadmill test, or exercise stress test, is designed to assess the heart's response to physical exertion.
During exercise, the heart muscle requires more oxygen. In individuals with coronary artery disease (CAD), narrowed arteries restrict blood flow, creating an oxygen supply-demand mismatch.
This lack of oxygen to the heart muscle, known as myocardial ischemia, specifically affects the subendocardial layer first.
Subendocardial ischemia is characteristically represented on an ECG as a downward shift of the ST segment, known as ST-segment depression.
As shown in the image, the ST segment is visibly below the isoelectric baseline, which is a classic positive finding during a stress test.

Option B: A prolonged PR interval signifies a delay in the electrical impulse traveling from the atria to the ventricles (an AV block). This is a conduction issue, not a typical sign of ischemia brought on by exercise.
Option C: A pathological Q wave is a marker of necrotic (dead) heart tissue from a previous myocardial infarction. It is a permanent ECG change and does not appear acutely during a stress test.
Option D: Hyperacute T waves are very tall, peaked T waves that are one of the earliest signs of an acute ST-elevation myocardial infarction (STEMI). While this is a sign of severe ischemia, the more common and expected finding for stable angina during a planned stress test is ST depression.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain ECG Interpretation in Exercise Stress Testing as background academic context rather than a clinical decision trigger.
Nurses are responsible for continuous patient monitoring during a treadmill test, including observing the ECG, blood pressure, and patient symptoms (e.g., chest pain, dyspnea, dizziness).
Prompt recognition of significant ST-segment depression is crucial for identifying a positive test, which indicates underlying coronary artery disease and helps guide further treatment to prevent a heart attack.
Patient safety is paramount. The nurse must know the criteria for stopping the test, such as severe chest pain, a significant drop in blood pressure, or dangerous arrhythmias.

How to Approach the Question

First, understand the purpose of a treadmill test: to stress the heart and unmask potential ischemia.
Recall the basic pathophysiology: increased exercise leads to increased myocardial oxygen demand. If supply is limited by coronary artery disease, ischemia occurs.
Connect the pathophysiology to the ECG. The most common type of ischemia induced by a stress test is subendocardial ischemia.
Remember the classic ECG sign for subendocardial ischemia: ST-segment depression.
Evaluate the other options by recalling what they represent: Prolonged PR (AV block), Q wave (old infarct), and Hyperacute T wave (early sign of STEMI). This process of elimination confirms ST depression as the correct answer for this context.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 2135-2136